sectional configuration of the nails 12 is an equilateral triangle having the edges thereof considerably rounded off at the corners as shown at 17 one side 18 in this arrangement forms the convex side of the curvature 12 while the opposite edge 19 is disposed on the concave site of the nail 11 as indicated by the circle 20 drawn in broken lines the nail 11 brings about a considerable material saving as opposed to a nail having a circular cross sectional area 20 without the moment of resistance being substantially reduced the cross section configuration shown in fig3 in addition offers the advantage that the nails may be better 34 packed 34 in the medullary canal as is furthermore to be derived from fig2 and 3 a recess 21 is formed in the straight distal end portion 14 the bottom surface of said recess extending approximately in parallel with the side 18 of the nail 11 a drive in tool may be brought into engagement with the recess 21 in order to drive the nail forward in the medullary canal or extract it from the medullary canal and perform during these movements in addition a rotary movement the remaining cross sectional area 23 easily suffices to withstand forces of rotation in this arrangement it is recommendable to select the transition of the cross sectional area 23 into the.