as illustrated in perspective view in fig1 an individual snow - guard 10 comprises three structural elements which are fixedly interconnected to produce a unitary article . the three structural elements are ( a ) a longitudinal laminar strap referred to generally by reference numeral 20 , ( b ) an upstanding snow - stop 30 , and ( c ) a unitary brace 40 , having a main body portion 40 &# 39 ; referred to in the art as a gusset . the strap 20 of a single thickness of sheet metal , has an up - roof end 21 , and a down - roof end 22 ( see fig2 ) which , when positioned on a shingle of a roof , lies inclined to the vertical plane , in the longitudinal direction , at a lower level than the up - roof end 21 . snow - stop 30 is fixedly secured to the down - roof end 22 of the strap 20 so that the snow - stop &# 39 ; s up - roof surface 31 stops snow ; the snow - stop &# 39 ; s down - roof surface 32 is braced by the brace 40 which is downwardly inclined . illustrated in fig2 a - 3d and 4a - 4d are blanks for the laminar longitudinal strap 20 , the snow - stop 30 and the unitary brace 40 , respectively , preferably formed from first , second and third foldable sheet metal elements which may be of the same weather - resistant metal or different , and of the same thicknesses or different , provided different metals are chosen not to have a deleterious effect in contact with one and another , and provided the thickness is no greater than 2 mm so as to be readily deformable . typically , the metal is stainless steel , copper , or galvanized steel , the latter two being most preferred . the preferred thickness of copper corresponds to sheet stock in the range from 16 oz / ft 2 ( ounces / square foot ) to 40 oz / ft 2 , most preferably 16 - 20 oz / ft 2 ; and the preferred thickness of galvanized steel corresponds to sheet stock in the range from 26 gauge to 18 gauge , most preferably 26 - 24 gauge . sheet stock having a thickness in the aforementioned ranges is foldable 180 ° upon itself to form a seam which has great strength . alternatively , the snow guard may be molded from a synthetic resinous material , for example recycled poly ( vinyl chloride ) ( pvc ) or acrylonitrile - butadiene - styrene ( abs ) resin . preferably reinforced with an inorganic fiber such as glass . referring to fig2 there is illustrated a laminar strap 20 having an up - roof end 21 and a down - roof end 22 at either end of a flat body portion 23 . the up - roof end is preferably adapted to be fixedly secured to the deck the roof and is provided with spaced apart through - apertures 24 for nailing or otherwise securing the strap to the deck . alternatively , the up - roof end may be bent over so as to enable it to be hooked onto the upper edge of a shingle . the down - roof end 22 is generally triangular or trapezoidal in shape , the sides of the triangle or trapezium being equally angulated in the range from about 10 ° to 45 ° to the longitudinal central axis of the strap , but oppositely directed . marginal strip portions 25 , 26 respectively of the down - roof end 22 are shown in phantom view defined by dotted fold lines 27 , 28 along which each strip portion is to be folded over , upwardly , through about 180 °. snow - stop 30 and brace 40 in abutting relationship are secured upon the down - roof end 22 by the folded - over marginal strip portions , conveniently determining that the width of the strap 20 be preferably the same as the width of the snow - stop 20 . reverting to fig1 the snow - stop 30 comprises an up - standing snow - restraining barrier 33 which is integral with , and arises vertically from , a basal flange , referred to as a barder - base 34 , fixedly secured to the upper surface of the strap 20 . viewed down - roof along the longitudinal axis of the strap , the barrier 33 has a generally arcuate shape , preferably an arcuate segment having an area in the range from semi - circular to about 25 % greater than semi - circular , and most preferably an approximately semi - circular configuration , the periphery of which is provided with flange means 35 which serves two functions : it provides rigidity to the circumferential portion of the barrier , and , it protects the down - roof surface 32 of the barrier against contact with water falling from above . such water is trapped interstitially in the meeting - plane of the down - roof surface 32 of barrier 33 and the up - roof surface of the brace 40 . the flange means 35 is most preferably a continuous peripheral flange , but may less preferably be provided by a series of circumferentially spaced apart tabs or &# 34 ; ears &# 34 ; projecting down - roof . though such tabs facilitate locking the arcuate flanges 43 , 44 to the barrier 33 , it will be evident that enhancement of the rigidity of the barrier will be diminished by not providing a substantially continuous peripheral flange , as will be the lack of adequate protection against water being trapped in the meeting - plane . if such tabs are used it is therefore necessary to provide them over at least one - half of the periphery , and preferably over a major portion of the periphery . as illustrated in fig1 the barrier 33 is preferably flanged to form a peripheral flange 35 along the entire arcuate periphery , and the barrier is most preferably an approximately semi - circular disc , as shown . the flange 35 projects down - roof for a distance sufficient to extend over the down - roof face of the barrier to protect the meeting - plane of the barrier &# 39 ; s down - roof surface 32 and the up - roof surfaces of the arcuate flanges of the brace . preferably , the flange extends down - roof for from about 2 mm ( 3 / 32 &# 34 ;) to 10 mm ( 3 / 8 &# 34 ;) past the down - roof surface 32 of the barrier 33 . in a preferred embodiment , the flange is beveled downward to provide an interference fit with vertically projecting arcuate segments , referred to as laminar arcuate flanges 43 , 44 ( see fig8 ) of the brace &# 39 ; s main body 40 &# 39 ;. alternatively , the peripheral flange is crimped over the laminar arcuate flanges 43 , 44 to secure their up - roof faces tightly against the down - roof face of the barrier 33 . the snow - stop 30 may be formed by casting bronze or cast iron so as to provide the desired flange , optionally beveled , but it will be evident that the flange on a cast snow - stop will not be crimped over the arcuate flanges of the brace . further , the barrier illustrated as a semi - circular disc may in addition include a fanciful decorative figure popular in the art , such as an eagle with its wings spread wide , or any other complementary geometric figure . referring to fig3 a , there is shown a shaped laminar blank 36a having a generally semi - circular disc portion 37a of a predetermined radius in the range from about 1 &# 34 ; ( 2 . 54 cm ) to about 3 &# 34 ; ( 7 . 6 cm ), most preferably in the range from about 1 . 25 &# 34 ; ( 3 . 2 cm ) to 2 &# 34 ; ( 5 cm ); and , a generally rectangular portion 38 shown in this view as having an arcuate edge 39 of large radius to deflect down - moving snow towards the sides of the barrier 33 , after it is formed . edge 39 is effective to deflect snow when the snow - stop is installed with its barrier sufficiently spaced - apart from an adjacent down - roof edge of a shingle as to expose the edge 39 and snow accumulates against the edge . dotted line 33 &# 39 ; a and arc 35 &# 39 ; a indicate where the blank is bent at right angles to provide the barrier - base 38 and peripheral flange 35 , respectively . referring to fig3 b , there is shown a laminar blank 36b for a snow - stop having the same rectangular base 38 with an arcuate edge 39 , but the snow - restraining surface of the semi - circular disc 37b is enlarged with a lower rectangular portion 18b . thus , when the blank is bent at right angles along the dotted line 33 &# 39 ; b , to form a barrier , it presents a lower rectangular portion and an upper semi - circular portion the combined height of which may be up to 3 &# 34 ; ( 7 . 6 cm ). as before , a peripheral flange is formed on the disc 37b by bending the peripheral margin downwards along the arc and sides 35 &# 39 ; b of the disc and rectangle respectively . referring to fig3 c , there is shown a laminar blank 36c for a snow - stop having the same rectangular base 38 with an arcuate edge 39 , but the semi - circular disc 37c is provided with projecting tabs 14 which are to be bent downwards behind the up - roof surface of the barrier , after it is formed . the sum of the widths of the tabs along the periphery is at least one - half , and preferably at least 75 % of the semi - circular periphery of the disc 37c . additional tabs 14 are provided on the barrier - base which locks the tabs in slots in the strap to fasten the snow - stop . referring to fig3 d , there is shown a shaped laminar blank 36d having an enlarged arcuate segment 37d , the area of the segment being defined by the secant ( dotted line 33 &# 39 ; d ) intersecting the periphery of the disc . as will be evident , the segment 37d affords a larger restraining surface than a semi - circle of the same radius without an increase in width of the laminar strap 20 . as before , the blank 36d is provided with rectangular portion 38 having arcuate edge 39 . dotted line 33 &# 39 ; d and arc 35 &# 39 ; d indicate where the blank is bent at right angles to provide the barrier - base 38 and peripheral flange 35 , respectively . reverting to fig1 the brace 40 comprises a tapered structural gusset which braces the snow - stop against the force exerted by packed snow . the shape of the brace may be that of a partial cone , typically about one - half of a cone so that the surface is a semi - conical surface , or , that of a pyramidal element , provided the brace includes upstanding substantially vertical laminar arcuate flanges 43 , 44 and laminar lateral flanges 45 , 46 projecting at equal angles in opposed directions , symmetrically about the vertical plane containing the longitudinal axis . preferably the main body 40 &# 39 ; comprises a gusset with twin triangular elements 41 and 42 having contiguous apexes intersecting near a vertical plane containing the longitudinal central axis of the strap 20 , the point of intersection being contiguous with the down - roof surface 32 of barrier 33 . each triangular element 41 , 42 has an arcuate upper flange 43 , 44 respectively . each arcuate upper flange has an arcuate periphery extending over substantially one - half of the circumference of a semi - circle circumscribed around oppositely disposed arcuate flanges . the radius of the periphery of each arcuate flange is preferably chosen to closely match the periphery 35 &# 39 ; a ( fig3 a ) of the peripheral flange 35 , lying closely adjacent thereto , so as to have the flange protect the planar interstitial space between the metal meeting surfaces of the barrier 33 and the vertical flanges 43 , 44 against entrapping damaging acid rain . by &# 34 ; meeting surfaces &# 34 ; i refer to the down - roof surface 32 of the barrier 33 and the up - roof surface of each arcuate flange 43 , 44 . a suitable radius which closely matches the periphery of the barrier 33 is in the range ± 20 % ( plus or minus twenty percent ) of the radius of the barrier 33 . most preferably the radius of the semi - circle confining the arcuate flanges is chosen to approximate the radius ± 10 % of the barrier 33 so that the arcuate flanges 43 and 44 are substantially coextensive with the periphery of the barrier and snugly fitted under the peripheral flange 35 . at least one , and preferably both , of the arcuate flanges 43 and 44 is preferably fixed in overlying contact with the down - roof surface 32 of the barrier 33 . the arcuate flanges 43 , 44 provide incremental thickness of metal near the periphery of the barrier 33 reinforcing the strength along the periphery . the triangular elements 41 , 42 are also provided with lateral flanges 45 , 46 respectively , projecting angularly in opposed directions . these flanges 45 , 46 are tightly secured in contact with the down - roof end 22 by the angulated marginal strip portions 25 , 26 which are folded over the flanges 45 , 46 . the radius of a gusset without vertical flanges is chosen in an analogous manner . referring to fig4 a , there is shown a laminar blank 47a having a generally trapezoidal main portion 48a and projecting tabs 43 &# 39 ; a and 44 &# 39 ; a . dotted line 51a indicates the line along which opposed halves 41 &# 39 ; a and 42 &# 39 ; a of the main portion 48a are bent downwardly to form the main body 40 &# 39 ; ( of brace 40 ) and triangular elements 41 and 42 , one the mirror - image of the other . dotted lines 52a and 53a indicate the lines along which opposed projecting tabs 43 &# 39 ; a and 44 &# 39 ; a of equal area , are bent upwardly to form laminar arcuate upward flange portions 43 and 44 respectively of the brace 40 . dotted lines 54a and 55a indicate the lines along which equally angulated but opposed marginal portions 45 &# 39 ; a and 46 &# 39 ; a are bent to project laterally . when marginal portions 45 &# 39 ; a and 46 &# 39 ; a are locked under the tightly folded angulated marginal strip portions 25 , 26 respectively of the down - roof end 22 , liquid impermeable seals are formed , and at the same time , the brace 40 is secured under flange means 35 and against the down - roof surface 32 of barrier 33 , preferably additionally , with button rivets 49 ( see fig8 ). the angles formed by the intersection of the edges of marginal portions 45 &# 39 ; and 46 &# 39 ; with the longitudinal axis 51 are each in the range from 25 ° to 45 ° with respect to the longitudinal axis . referring to fig4 b , there is shown a laminar blank 47b having a generally trapezoidal main portion 48b and projecting tabs 43 &# 39 ; b and 44 &# 39 ; b . dotted line 51b indicates the line along which opposed halves 41 &# 39 ; b and 42 &# 39 ; b of the main portion 48b are bent downwardly to form the main body 40 &# 39 ; ( of brace 40 ) and triangular elements 41 and 42 , one the mirror - image of the other . dotted lines 52b and 53b indicate the lines along which opposed projecting tabs 43 &# 39 ; b and 44 &# 39 ; b are bent upwardly to form laminar arcuate upward flange portions 43 and 44 respectively of the brace 40 . the radial lines dividing the segments 43 &# 39 ; b and 44 &# 39 ; b represent slits between the portions of the segments , which slits are extensions of the radial lines along which the plural triangular elements of the gusset ( two are formed on each side of the longitudinal axis ). dotted lines 54b and 55b indicate the lines along which equally angulated but opposed marginal portions 45 &# 39 ; b and 46 &# 39 ; b are bent to project laterally . as before , when marginal portions 45 &# 39 ; b and 46 &# 39 ; b are locked under the tightly folded angulated marginal strip portions 25 , 26 respectively of the down - roof end 22 , liquid impermeable seals are formed , and at the same time , the brace 40 is secured under flange means 35 and against the down - roof surface 32 of barrier 33 , preferably additionally , with button rivets 49 . referring to fig4 c , there is shown a laminar blank 47c analogous to that shown in fig4 b , blank 47c having a generally trapezoidal main portion 48b and projecting tabs 43 &# 39 ; b and 44 &# 39 ; b , except that blank 47c is to be formed into a main body having a gusset with six triangular elements . referring to fig4 d , there is shown a laminar blank 47d having a generally pie - shaped main portion 48b which is to be formed into a gusset having a conical shape . no projecting tabs are shown projecting from the main portion 48b , though such tabs may be provided if desired . as before , dotted lines 54d and 55d indicate the lines along which equally angulated but opposed marginal portions 45 &# 39 ; d and 46 &# 39 ; d are bent to project laterally and be secured tightly under angulated marginal strip portions 25 , 26 respectively of the down - roof end 22 , to form liquid impermeable seals , at the same time securing the brace 40 under flange means 35 and against the down - roof surface 32 of barrier 33 . as illustrated in fig5 snow guards 10 are disposed on a conventional pitched roof overlaid by rectangular laminar tiles or slate 16 in spaced - apart relationship , preferably regularly , and enough snow guards are used so that , cooperatively , they prevent packed snow accumulated on the roof from suddenly sliding off the roof and causing injury to gutters , or to shrubs and plants beneath the roof &# 39 ; s edge , or to any person who happened to be positioned so unfortunately . a snow guard 10 is installed so that its laminar strap 20 may be inserted and secured between shingles of overlapping adjacent courses r p and r q . in a typical slate roof wherein successive courses r p , r q and r r are &# 34 ; double - layered &# 34 ; slates 16 , each about 18 &# 34 ; ( 45 . 7 cm ) long and 9 &# 34 ; ( 22 . 8 cm ) wide , slates in course r p have their lower portions exposed over about 7 . 5 &# 34 ; ( 19 cm ), a slate from the next adjacent course r q covers the slates in course r p over a distance of about 7 . 5 &# 34 ; ( 19 cm ) and slates from course r r overlap the up - roof ends of slates in course r p over a distance of about 3 &# 34 ; ( 7 . 6 cm ). the laminar strap 20 is positioned over the upper surface of a slate the corners of which are identified by numerals 1 , 2 , 3 , 4 so that up - roof end 21 extends beyond the up - roof edge of a slate exposed in course r p , and under the lower portion of a slate in row r r . the up - roof end 21 is nailed with nails 15a ( see fig6 ) through apertures 24 , stapled , screwed or otherwise fixedly secured directly to the roof &# 39 ; s deck which is typically wood planks , or a composite veneer laminate , or weather - proof plywood . when thus secured along the longitudinal axis of a slate midway between its side edges , strap 20 rests substantially flat on the upper surface of the shingle in course r p , about 7 . 5 &# 34 ; of which ( longitudinally ) is exposed , the snow - stop 30 being disposed adjacent the down - roof edges of contiguous slates in course r q . the strap 20 , as shown , lies beneath the contiguous edges of the slates in course r q , but may equally be positioned between the contiguous edges of two slates in row r q . additional snow guards 10 are similarly positioned on slates in alternate courses r p , r r , etc . in fig6 there is illustrated a cross - sectional view in side elevation , of the conventional slate roof having a series of snow guards spaced apart both laterally and vertically at regular intervals upon the slates in consecutive rows r p , r q , and r r on a newly installed slate roof . as seen , the up - roof ends 21 are directly fastened to the roof &# 39 ; s deck with nails 15a the heads of which are flush - driven against the upper surface of the strap 20 secured to the roof - deck . the brace 40 prevents the barrier 33 from pivoting backwards thus essentially eliminating the bowing of the strap 20 , and negating the breakage of slate when the snow guard is subjected to high forces exerted by an accumulated snow - pack . when nail 15b is driven through an aperture in a slate 16 , and a snow guard hung ( not shown ) from that slate , a load against the snow - stop will bow the strap and nail 15b provides a fulcrum , causing the slate to break . the effect of the force is magnified because the shank of the nail projects above the surface of the deck for a distance which is approximately twice the thickness of the slate 16 . the bending moment due to forces exerted at the head of the nail by the weight of an accumulated snow - pack commencing to slide is therefore much greater than the bending moment exerted on nail 15a . illustrated in fig7 is a roof protected with shingles made from a reinforced organic substrate such as glass fiber reinforced ( gfr ) asphalt , or gfr synthetic resinous material such as recycled poly ( vinyl chloride ) ( pvc ) or acrylonitrile - butadiene - styrene ( abs ) resin . a snow guard 10 is positioned on a lower course of asphalt shingles r x with the up - roof end 21 nailed directly to the roof &# 39 ; s deck . the length of strap 20 &# 39 ; is much shorter than that of strap 20 because snow - stop 30 is positioned adjacent the next adjacent upper course of shingles r y which typically overlaps the up - roof portion of shingles in course r x only about 2 &# 34 ; ( 5 . 1 cm ). referring to fig8 there is shown an end elevational view of the snow guard 10 , viewed up - roof along the longitudinal axis . it is seen that the angulated triangular surfaces of triangular elements 41 and 42 slope downwardly and symmetrically from either side of the longitudinal axis 51 . in plan view , each triangle is an isosceles triangle having one short side , the other two being longer and of equal length . the long side coincides with the longitudinal axis 51 and the short sides 52 , 53 are oppositely directed but equally inclined at an included angle α in the range from 45 ° to 60 °. by &# 34 ; included angle &# 34 ; is meant the angle included by the intersection of the triangular surfaces of triangular elements 41 and 42 . the short sides of the isosceles triangles intersect in the vertical plane containing the longitudinal axis so as to be free from a gap providing access to the cavity formed beneath the brace . further , the intersection is beneath the peripheral flange 35 so as to have a meeting - plane of the laminar arcuate flanges 43 and 44 protected from falling rain . the laminar arcuate flanges 43 and 44 are tightly fastened to the down - roof surface 32 of barrier 33 , preferably by button - rivets 49 . in addition to providing a meeting - plane which is protected from rain by the peripheral flange 35 , laminar arcuate flanges 43 and 44 reinforce essentially all the area of the barrier 33 lying outside the pyramidal base formed by the triangular elements 41 , 42 and the triangular portion of the down - roof end 22 ( of the strap 20 ) beneath the gusset 40 . the unitary structure formed by the brace 40 and snow - stop 40 is thus provided with liquid - impermeable edges and the pyramid - shaped cavity formed by the triangular elements 41 , 42 and the upper surface of down - roof end 22 is thus sealed against water , greatly slowing the internal weathering of the brace and enhancing the expected useful life of the snow guard . referring now to fig9 there is shown a plan view of an individual prior art snow - guard 110 which comprises three structural elements fixedly interconnected to produce a unitary article . the three structural elements are ( a ) a longitudinal laminar strap referred to generally by reference numeral 120 , ( b ) an upstanding snow - stop 130 , and ( c ) a unitary brace 140 , having a main body portion 140 &# 39 ; referred to in the art as a gusset . the strap 120 of a single thickness of sheet metal , has an up - roof end 121 , and a down - roof end 122 which , when positioned on a shingle of a roof , lies in the longitudinal direction at a lower level than the up - roof end 121 . snow - stop 130 and brace 140 are fixedly secured to the down - roof end 122 of the strap 120 so that the snow - stop &# 39 ; s up - roof surface 131 stops snow ; the snow - stop &# 39 ; s down - roof surface 132 is braced by the brace 140 which is downwardly inclined . the snow - stop 130 comprises an up - standing snow - restraining barrier 133 which is integral with , and arises vertically from barrier - base 134 which is secured to the upper surface of the strap 120 . viewed down - roof along the longitudinal axis of the strap , the barrier 133 has a generally semi - circular configuration , the periphery of which is that of a portion of a planar disc . when brace 140 is secured to the down - roof surface 132 of the barrier 133 with fastening means such as button rivets 49 , the trapezoidal flanges 143 , 144 lie in contact with that surface except for a small central axial portion of the brace between the trapezoidal flanges which is spaced away from the down - roof surface 132 of barrier 133 , forming a gap 50 . this gap provides a through - passage for entry of water into the cavity beneath the brace 140 . note also that the upper edges of the flanges 143 and 144 are spaced apart from the periphery of the barrier 133 . thus both the gap and the meeting plane of the flanges 143 and 144 with the down - roof surface of the barrier are unprotected . referring to fig1 and 11 there is shown an end elevational view of the snow guard , and a plan view of a blank from which the brace 140 is formed , analogous to the views shown in fig8 and 4 respectively . the brace 140 is formed from a tapered laminar blank 147 shown in fig1 . the blank 147 is symmetrical about a longitudinal axis 151 along which opposed halves 141 &# 39 ; and 142 &# 39 ; of the main portion 148 are bent downwardly to form triangular elements 141 and 142 , one the mirror image of the other . dotted lines 152 and 153 indicate the lines along which opposed projecting trapezoidal tabs 143 &# 39 ; and 144 &# 39 ; of equal area , are bent upwardly to form upward trapezoidal flange portions 143 and 144 respectively . as before , dotted lines 154 and 155 indicate the lines along which equally angulated but opposed marginal portions 145 &# 39 ; and 146 &# 39 ; are bent to project laterally . referring to fig9 and 11 it is seen that trapezoidal flanges 143 and 144 of the brace 140 are secured against the down - roof surface 132 of the barrier 133 , preferably with button rivets 49 . when the marginal strip portions 125 , 126 are folded over marginal portions 145 &# 39 ;, 146 &# 39 ; respectively of the down - roof end 122 , liquid impermeable seals are formed which trap water entering the gap . also as before , the angles formed by the intersection of the edges of marginal portions 145 &# 39 ; and 146 &# 39 ; with the longitudinal axis 151 are each in the range from 25 ° to 45 ° with respect to the longitudinal axis . referring to fig1 there is schematically illustrated a snow guard 210 in which the laminar strap 20 , and snow - stop 30 are substantially identical except that the brace 40 ( with a gusseted main body 40 &# 39 ; of pyramidal shape ) in the snow guard 10 is substituted by a brace 240 having a gusseted main body 240 &# 39 ; with a conical shape . the main body 240 &# 39 ; is formed from laminar blank 47d illustrated in fig4 d . the blank is shaped so that the radius of its periphery is slightly less than the radius of the down - roof surface 32 of barrier 33 , preferably in the range from 1 to 10 % less so that the periphery of the conical gusset lies closely adjacent to the periphery of the barrier 33 . as before , the main body 240 &# 39 ; is provided with angulated oppositely directed laminar lateral flanges 245 and 246 which are locked under angulated side edges 25 and 26 of the down - roof portion 22 of strap 20 . when so locked , the arcuate periphery of the conical gusset snugly abuts the down - roof surface 32 of the barrier 33 , reinforcing the periphery of the barrier against forces exerted in the down - roof direction against the snow - stop 30 . if desired , the arcuate periphery of the blank 47d may be provided with projecting tabs ( not shown ) which may be inserted through mating slots in the barrier 33 , and the inserted tabs turned down against the up - roof surface of the barrier 33 . having thus provided a general discussion , described the overall snow guard in detail particularly in comparison with the most relevant prior art , and illustrated the invention with specific examples of the best mode of making and using the snow guard , it will be evident that the invention has provided an effective improvement of a recent solution to an age - old problem . it is therefore to be understood that no undue restrictions are to be imposed by reason of the specific embodiments illustrated and discussed , and particularly that the invention is not restricted to a slavish adherence to the details set forth herein .