with reference to the drawing , fig1 thereof illustrates an electrical junction box 10 , here showing a metal conduit 12 having a threaded end 13 that penetrates through an opening on one side wall 14 . a six - lug lock nut 15 has a female thread that mates with the spiral thread on the conduit end 13 , and this is turned down into contact with the wall 14 . on each lug 16 of the lock - nut there is a sharp edge or flange that cuts into the metal surface of the wall 14 when the lock nut is twisted down tightly , and this makes electrical contact between the conduit 12 and the junction box 10 , and also locks the lock nut 12 against rotation . however , in order to tighten the lock nut securely , some tool needs to be used . unfortunately , the electrician traditionally uses a screwdriver and hammers it to tighten the lock nuts , placing the screwdriver blade against one of the lock - nut lugs and then rapping against the handle of the screwdriver . as also shown here , there can typically be a flange or rim 17 on the open side of the junction box 10 , and with this flange being above the plane of the lock nut 15 , the flange 17 can obstruct access to the lock nut 15 , making it even more difficult to tighten . in some electrical boxes , the back or side walls , or other internal structure , can also get in the way of a typical style of wrench , making it difficult to turn the lock nut . [ 0020 ] fig1 also shows electrical wires 18 that may be carried through the conduit 12 , and which are connected to devices or other electrical wires ( not shown ) within the box 10 . a lock - nut wrench 20 according to one embodiment of the invention is shown in fig2 and 3 . this wrench 20 is unitarily formed , i . e ., it is of one - piece metal construction , with the wrench having an elongated handle 22 and a head 24 situated at one end , to wit a distal end , of the handle 22 . the handle 22 is generally flat ( fig3 ) and preferably has serrations 25 formed along one edge as finger grips . a plastic coating 26 covers the handle 22 for comfort and to facilitate gripping and also is an insulator to help prevent shocks if the wrench 20 should make [ 0022 ] fig6 and 7 are plan and side views , respectively , of a lock nut wrench according to another embodiment of the invention . [ 0023 ] fig8 is a top plan view of an embodiment which is adapted to receive a square - drive socket wrench handle . with reference to the drawing , fig1 thereof illustrates an electrical junction box 10 , here showing a metal conduit 12 having a threaded end 13 that penetrates through an opening on one side wall 14 . a six - lug lock nut 15 has a female thread that mates with the spiral thread on the conduit end 13 , and this is turned down into contact with the wall 14 . on each lug 16 of the lock - nut there is a sharp edge or flange that cuts into the metal surface of the wall 14 when the lock nut is twisted down tightly , and this makes electrical contact between the conduit 12 and the junction box 10 , and also locks the lock nut 12 against rotation . however , in order to tighten the lock nut securely , some tool needs to be used . unfortunately , the electrician traditionally uses a screwdriver and hammers it to tighten the lock nuts , placing the screwdriver blade against one of the lock - nut lugs and then rapping against the handle of the screwdriver . as also shown here , there can typically be a flange or rim 17 on the open side of the junction box 10 , and with this flange being above the plane of the lock nut 15 , the flange 17 can obstruct access to the lock nut 15 , making it even more difficult to tighten . in some electrical boxes , the back or side walls , or other internal structure , can also get in the way of a typical style of wrench , making it difficult to turn the lock nut . [ 0026 ] fig1 also shows electrical wires 18 that may be carried through the conduit 12 , and which are connected to devices or other electrical wires ( not shown ) within the box 10 . a lock - nut wrench 20 according to one embodiment of the invention is shown in fig2 and 3 . this wrench 20 is unitarily formed , i . e ., it is of one - piece metal construction , with the wrench having an elongated handle 22 and a head 24 situated at one end , to wit a distal end , of the handle 22 . the handle 22 is generally flat ( fig3 ) and preferably has serrations 25 formed along one edge as finger grips . a plastic coating 26 covers the handle 22 for comfort and to facilitate gripping and also is an insulator to help prevent shocks if the wrench 20 should make contact with a live ( electrified ) metal surface , or with an electrically hot wire . an offset or double bend 27 is provided at the distal end so that the head 24 lies in a plane that is parallel to that of the handle 22 , but is offset by a sufficient amount to allow the wrench to clear the flange or rim 17 of the junction box 10 . in other embodiments , the handle can be angled slightly to moderately . the head 24 is adapted for fitting over and engaging the lock nut 15 , and is generally of a round shape with two arcuate jaws 28 and 29 that bow out from the center where the head meets the handle . each of the jaws has a first tooth 30 that is oriented radially inward at the distal end of the respective jaw . each jaw 28 , 29 has a second tooth 31 that is spaced somewhat to the proximal side of the first tooth , so that there is a space or gap 32 between the respective first and second teeth 30 , 31 . an arcuate surface 33 continues across the inside of the head 24 from the second tooth 32 of one jaw 28 to the second tooth 31 of the other jaw 29 . the ends of the two jaws 28 and 29 define a gap 35 between one another of sufficient width to allow the head 24 to be placed over the conduit 12 so that the teeth and gaps thereon can engage the lock nut 15 . here the gap 35 and the arcuate surface 33 are centered on the axis of the handle 22 . the jaws 28 , 29 are also hog - nosed , that is , they end at a more - or - less transverse line after the outer edge of the first tooth 30 . this shortens the jaw as much as possible , and permits a greater amount of angular throw when tightening the lock nut . also , because a laser machining process can be used to form these from a steel sheet or plate , the jaws 28 , 29 can be made rather narrow without sacrifice of strength , which also facilitates use of the wrench in tight locations . the corners of the teeth 30 and 31 that are adjacent the space 32 between them are sharp edged , that is , with a zero radius . this feature ensures that the wrench does not slip off the lugs , but rather captures them and contains the lock nut . the arcuate surface 33 meets the outer edges of the lugs that are facing it , and this feature combines with the capturing of the lugs within the spaces 32 , so that the wrench acts as a spanner , and will contain and turn the lock nut 15 , even where the lock nut is of very thin metal . [ 0030 ] fig4 illustrates the lock - nut wrench 20 being used on a six - lug or six - ear lock nut 15 . here there are six lugs 16 spaced at sixty - degree intervals , so there are two lugs diagonally opposite each other . the wrench head fits directly over the nut 15 , with two of the lugs 16 fitting into the gaps or spaces 32 between the first and second teeth 30 , 31 , and with two of the lugs 16 fitting against the arcuate wall 33 . fig5 shows the same wrench used on an eight - lug lock nut 15 a , i . e ., a lock nut with eight lugs 16 a spaced at forty - five degree intervals . two of the lugs 16 a are captured in the spaces or gaps 32 between the first and second teeth 30 , 31 , and three lugs 16 a fit against the arcuate wall 33 . other lock nuts besides those shown here could also be accommodated . the wrench 20 is as easy to use on a lock nut as the familiar open wrench is on a regular hex head bolt . another lock nut wrench 40 according to an alternative embodiment of this invention is shown in fig6 and 7 . here , the wrench is a double ended , open wrench to accommodate two different sizes of lock nuts . the wrench 40 has a central handle portion 42 , with a first open head 44 at one end and a second open head 144 at the other end , with first and second offsets 45 , 145 joining the heads 44 , 144 to the handle portion 42 . as in the first embodiment each head has a pair of arcuate jaws 45 , 46 and 145 , 146 , with a first tooth at the outer or proximal end , and a second tooth spaced in from the first tooth to define a gap to capture a lug of the lock nut . there is a gap or space 50 , 150 between the two jaws for each head , and here these are oriented to one side , rather than in line with the axis of the handle as was the case in the embodiment of fig3 and 4 . in this embodiment , there is an arcuate spanner surface 133 . in other possible embodiments , additional teeth could be provided so that there are spaces for all of the lock - nut lugs except those that are situated in the gaps 50 , 150 , but the illustrated embodiments are preferred over that construction . the handle portion 42 can be given a plastic coating , if desired . also , as in the first embodiment , the ends of the jaws are hog - nosed for optimal turning angle . another possible embodiment , adapted for a square drive handle ( the latter not shown ) is illustrated in fig8 . here , the lock nut wrench 20 ′ has a head portion 24 ′, with a pair of jaws 29 ′ and 30 ′ as described previously , as well as a square - drive receiving tab 22 ′ that projects from the head portion 24 ′. the tab 22 ′ can be offset above the plane of the head 24 ′. the tab can be made to accept quarter - inch , three - eighths - inch , or other size square drive , or to accept a hex drive . a male member can be provided instead of a square or hex socket , so as to permit use of a female or tubular drive member , e . g ., a hand - held power drill or driver . it should be understood that the illustrated wrenches are each shown for particular sizes of lock nuts , but are representative of wrenches of a range of sizes . it is expected that the electrician would be provided with a set of wrenches each of a given size , so as to accommodate all common sizes of lock nuts , and so that these tools can be used on an extensive range of conduit sizes . while the invention has been described hereinabove with reference to selected preferred embodiments , it should be recognized that the invention is not limited to those embodiments . rather , many modification and variations would present themselves to persons skilled in the art without departing from the scope and spirit of this invention , as defined in the appended claims .