A surgical stapling loading unit including a first jaw and a second jaw movable relative to one another to perform a surgical stapling operation whereby staples are fired into target tissue, the loading unit comprising: a cartridge assembly supportable on one of the first jaw and the second jaw, the cartridge assembly having a tissue contacting surface defining a longitudinally extending elongate slot and a plurality of staple retaining slots formed therein, wherein the cartridge assembly includes a surgical staple loaded into each staple retaining slot; an anvil assembly supported on another of the first jaw and the second jaw, the anvil assembly including an anvil plate having a tissue contacting surface defining a longitudinally extending elongate slot and a plurality of staple forming pockets; a surgical buttress releasably disposed against at least one of the tissue contacting surface of the cartridge assembly and the tissue contacting surface of the anvil assembly, the or each surgical buttress including a body portion configured and dimensioned to overlie either the plurality of staple retaining slots or the plurality of staple forming pockets of the respective cartridge assembly and anvil assembly, the body portion defining a distal edge and a proximal edge; a respective length of suture ("S2") securing a respective surgical buttress against the at least one of the tissue contacting surface of the cartridge assembly and the tissue contacting surface of the anvil assembly, wherein the suture extends transversely across the respective surgical buttress; and a retaining feature securing the length of suture to the respective cartridge assembly and anvil assembly wherein the retaining feature comprises a plurality of grooves formed in a side surface of the respective cartridge assembly and anvil assembly, wherein the grooves are formed near opposed distal side edges and opposed proximal side edges of the respective cartridge assembly and anvil assembly; and characterised in that portions of the length of suture are threaded through the surgical buttress along opposed sides of the surgical buttress and in that each groove is configured and dimensioned to receive, and is in receipt of, a length of the length of suture therein. a cartridge assembly supportable on one of the first jaw and the second jaw, the cartridge assembly having a tissue contacting surface defining a longitudinally extending elongate slot and a plurality of staple retaining slots formed therein, wherein the cartridge assembly includes a surgical staple loaded into each staple retaining slot; an anvil assembly supported on another of the first jaw and the second jaw, the anvil assembly including an anvil plate having a tissue contacting surface defining a longitudinally extending elongate slot and a plurality of staple forming pockets; a surgical buttress releasably disposed against at least one of the tissue contacting surface of the cartridge assembly and the tissue contacting surface of the anvil assembly, the or each surgical buttress including a body portion configured and dimensioned to overlie either the plurality of staple retaining slots or the plurality of staple forming pockets of the respective cartridge assembly and anvil assembly, the body portion defining a distal edge and a proximal edge; a respective length of suture ("S2") securing a respective surgical buttress against the at least one of the tissue contacting surface of the cartridge assembly and the tissue contacting surface of the anvil assembly, wherein the suture extends transversely across the respective surgical buttress; and a retaining feature securing the length of suture to the respective cartridge assembly and anvil assembly wherein the retaining feature comprises a plurality of grooves formed in a side surface of the respective cartridge assembly and anvil assembly, wherein the grooves are formed near opposed distal side edges and opposed proximal side edges of the respective cartridge assembly and anvil assembly; and characterised in that portions of the length of suture are threaded through the surgical buttress along opposed sides of the surgical buttress and in that each groove is configured and dimensioned to receive, and is in receipt of, a length of the length of suture therein.