A clinching mechanism (28) for bending the legs of a staple and stapler apparatus incorporating such a mechanism. The clinching mechanism (28) includes two pivotal ears (45, 46) each of which is formed with a cutting edge (70, 71) which cooperates with a fixed cutting edge (72, 73) arranged to cut the excess portions of staple legs. The length of the portions cut off is in accordance with the thickness of the set being stapled, the thinner the set, the longer the portions.