A surgical stapler is provided having a pair of jaws including a staple containing cartridge (522) and an anvil. Buttress material (526) is releaseable affixed to the staple containing cartridge by a cartridge retention system (500,600) prior to the stapling of tissue. At least one projection (532,632) is provided at a first or proximal end of the staple cartridge (522,622) and a groove (530,630) is formed at a second or distal end thereof. The staple cartridge (522,622) may include at least two projections (532,632) provided on either side of a knife slot (540,640). The buttress material (526,626) includes at least one aperture (531,631) for the receipt of a respective one of the projections (532,632) and a tab (535,635) at a distal end thereof configured to engage the groove (530,630).
