referring to fig1 to 5 of the drawings , wherein the invention , for the purposes of explanation , is disclosed as embodied in a type of clamp shown in u . s . pat . no . 1 , 529 , 281 of j . l . taylor , such clamp may be seen as including a pair of spaced parallel rails 10 and 12 . the rails are rigidly connected at one end as by bolts 14 to a head 16 providing a fixed clamp jaw 18 , and at their other ends are rigidily secured together as by bolts and a spacer block ( not shown ) which may be formed for connection to the cross rods of a clamp carrier such as shown in u . s . pat . no . 1 , 320 , 808 of j . l . taylor . the head 16 carries a known type of screw mechanism 20 such as shown in u . s . pat . no . 3 , 488 , 046 which is connected at 22 to a draw bar 24 for a movable jaw 26 slidably mounted on the rails 10 and 12 to move toward and away from the fixed jaw for clamping stock to be glued between the jaws . the movable jaw 26 is adjustably connected to the draw bar by a latch 28 pivotally mounted between its ends on the movable jaws and having a free end normally biased by a spring 29 into any one of a plurality of holes 30 in the draw bar 24 . each of the jaws 18 and 26 is provided with a jaw adapter 32 which is constructed according to the invention and may be substantially the same for both jaws . each jaw adapter includes like parallel side plates 34 with mutually perpendicular arms 36 and 38 . one of the side plates 34 of each jaw adapter is located to one side of the guide rails of the clamp and the other side plate is located on the other side of the rails as shown . the arms 36 of each jaw adapter extend upright from the rails and have a plate 40 welded or otherwise suitable secured to them . a face plate 42 , such as shown for example in the aforementioned copending patent application ser . no . 647 , 041 , is attached to plate 40 and both are supported on the arms 36 . the face plate 42 is attached to plate 40 for rocking motion as with identical brackets 44 and a spring 46 in the manner of said patent application such that the plate 42 may rock about a horizontal axis between upper and lower edges to engage and distribute pressure practically evenly to upper and lower edges of clamped board stock . the brackets 44 may be rendered vertically adjustable on plate 40 in the manner shown in said patent application to accomodate the face plate 42 to different heights of stock . the arms 36 rotatably support a roller 48 in a position to contact the top side of rails 10 and 12 . arms 38 of each jaw adapter extend parallel to the rails 10 and 12 and rotatably suport a roller 50 in a position to contact the bottom side of the rails . a transverse member 52 affixed to plate 40 on each jaw adapter and in contact with the top side of the rails 10 and 12 prevents during the absence of any clamping force on the jaw adapter , any pivoting thereof on the rails of the clamp in a direction tilting the arms 34 away from the jaws of the clamp . during the clamping of board stock the stock is engaged by the rockable face plate 42 on the front of each jaw adapter 32 and back edges of the jaw adapters engage the jaws of the clamp . the jaws 18 and 26 are each engaged throughout their entire height as shown . rollers 50 resist any tendency of the jaw adapters to pivot on the rails in a direction tending to urge the arms 36 against the top edge portions of the jaws . clamping forces are therefor distributed substantially evenly throughout the height of the jaws where contacted by the jaw adapters . by avoiding the application of clamping pressure primarily to the top edge portions of the jaws of the clamp the liklihood of the jaws being damaged in use is slight . also because of the way in which the jaw adapters are mounted on the rails 10 and 12 , that is , with the rollers 48 and 50 , the jaw adapters may be moved on the rails with little frictional resistance and greater clamping force than would otherwise be possible can be exerted on stock between them . the rollers 50 may be readily detached from the jaw adapters 32 by pulling the roller shafts 53 out of the side plates 34 after first removing cotter pins 54 , and in this way the jaw adapters are prepared for removal from or attachment to the claim . although a preferred form or the invention has been shown and described herein it is to be understood that various changes in and modifications of the disclosed construction may be made by one skilled in the art without departing from the spirit and scope of the invention . in particular the jaw adapters may be constructed to engage the jaws at lower edge portions to permit clamping forces to be transmitted to lower parts of the jaws rather than throughout their entire height . also , pins affixed in the arms 36 may be substituted for the rollers 48 , and as a further economy measure other pins detachable from and preferably rotatable in the arms 38 may be used in place of the rollers 50 . numerous other changes and modifications will occur to persons skilled in the art and are within the spirit and scope of the invention as defined by the annexed claims .