An end effector for a surgical instrument, comprising: a first jaw having a cartridge with a plurality of staple cavities configured to seat staples therein, the staple cavities opening on a tissue-facing surface of the cartridge; a second jaw opposing the first jaw and having an anvil with a plurality of staple forming cavities formed on a tissue-facing surface thereof, wherein the first and second jaws are configured to clamp tissue therebetween; an attachment feature comprising a retaining filament having an intermediate portion; first and second ends (112a, 112b) disposed on opposed sides of the intermediate portion, each of the first and second ends (112a, 112b) having an end feature configured to mate with at least one jaw of the first and second jaws; and an adjunct material releasably retained on the at least one jaw by the attachment feature that is arranged such that at least a part of the intermediate portion is disposed over the adjunct material and such that the first and second ends (112a, 112b) are spaced apart, the end effector further comprising at least one first retaining member disposed at one side of a tissue-facing surface of the at least one jaw in proximity to one edge of the tissue-facing surface of the at least one jaw, and at least one second retaining member disposed at another, opposed side of the tissue-facing surface of the at least one jaw in proximity to another, opposed edge of the tissue-facing surface, the first and second retaining members (118a, 118b) being configured to engage the part of the intermediate portion disposed over the adjunct material, characterized in that at least one of the first and second retaining members (118a, 118b) comprises a pair of adjacent posts (122d, 122p), each configured to engage at least a part of the intermediate portion of the retaining filament. a first jaw having a cartridge with a plurality of staple cavities configured to seat staples therein, the staple cavities opening on a tissue-facing surface of the cartridge; a second jaw opposing the first jaw and having an anvil with a plurality of staple forming cavities formed on a tissue-facing surface thereof, wherein the first and second jaws are configured to clamp tissue therebetween; an attachment feature comprising a retaining filament having an intermediate portion; first and second ends (112a, 112b) disposed on opposed sides of the intermediate portion, each of the first and second ends (112a, 112b) having an end feature configured to mate with at least one jaw of the first and second jaws; and an adjunct material releasably retained on the at least one jaw by the attachment feature that is arranged such that at least a part of the intermediate portion is disposed over the adjunct material and such that the first and second ends (112a, 112b) are spaced apart, the end effector further comprising at least one first retaining member disposed at one side of a tissue-facing surface of the at least one jaw in proximity to one edge of the tissue-facing surface of the at least one jaw, and at least one second retaining member disposed at another, opposed side of the tissue-facing surface of the at least one jaw in proximity to another, opposed edge of the tissue-facing surface, the first and second retaining members (118a, 118b) being configured to engage the part of the intermediate portion disposed over the adjunct material, characterized in that at least one of the first and second retaining members (118a, 118b) comprises a pair of adjacent posts (122d, 122p), each configured to engage at least a part of the intermediate portion of the retaining filament.