A system is disclosed. The system can comprise a replaceable staple cartridge comprising a plurality of staples, a proximal laterally-protruding lug, and a distal laterally-protruding lug. The system can further comprise a channel configured to receive the replaceable staple cartridge, wherein the channel comprises a sidewall comprising a proximal receptacle positioned and dimensioned to receive the proximal laterally-protruding lug and a distal receptacle positioned and dimensioned to receive the distal laterally-protruding lug.