and the pair of blades 73 74 a generally u shaped slot 75 is positioned between the blade member 73 74 the horizontal section 76 has a generally flat upper surface 77 each of the blades 73 74 provides a respective inclined cutting edge 78 79 the cutting edge 78 begins at pointed distal end 80 and extends to horizontal surface 84 of section 76 the inclined cutting edge 79 begins at pointed distal end 81 of blade 74 and extend to horizontal surface 84 of section 76 a plurality of notches or stepped portions 85 90 can be seen along each of the inclined cutting surfaces 78 79 of the blades 73 74 each of the stepped portions 85 90 includes a vertical surface 91 and a horizonal surface 92 the step portions combined with the size of slot 20 of trial tray 11 to limit the depth of cut that is made by the fin punch 71 the punch 71 only goes down to that particular stepped portion or notch 85 90 that can be fitted through the slot 20 depending upon the width of the slot 20 for example the punch 71 only goes down to the fourth notch for a size 34 4 34 tibial prep plate 11 because the slots 20 in the trial plate 11 for a size 34 4 34 or a given distance wide they would be provided as wider slots 20 for example on sizes 34 5 34 and 34 6 34 the slot 20 would be smaller for an over all width for a size 34 3 34 or.