A fastener cartridge (110, 210) for use with a surgical fastening instrument, the surgical fastening instrument including an anvil, a movable firing member (140, 240), and a firing lockout configured to prevent the movement of the firing member (140, 240) toward a distal end of said fastener cartridge (110, 210), said fastener cartridge (110, 210) comprising: a distal end; a cartridge body comprising a deck and a plurality of fastener cavities; a plurality of fasteners at least partially positioned within said fastener cavities; a layer positioned relative to said deck; and a sled (130, 230) movable between an unfired position and a fired position during a firing stroke of the firing member (140, 240), wherein said sled (130, 230) is configured to lift said fasteners toward the anvil during said firing stroke, wherein said sled (130, 230) is releasably engaged with said layer when said sled (130, 230) is in said unfired position, characterised in that said sled (130, 230) comprises a first configuration and a second configuration, wherein said sled (130, 230) is configured to hold the firing member (140, 240) out of engagement with the firing lockout when said sled (130, 230) is in said first configuration thereby allowing the movement of the firing member (140, 240) towards the distal end of said fastener cartridge, wherein said sled (130, 230) is unable to hold the firing member (140, 240) out of engagement with the firing lockout when said sled (130, 230) is in said second configuration thereby preventing the movement of the firing member (140, 240) towards the distal end of said fastener cartridge (110, 210), and wherein said sled (130, 230) is configured to enter into said second configuration if said layer is pulled away from said deck prior to said firing stroke. a distal end; a cartridge body comprising a deck and a plurality of fastener cavities; a plurality of fasteners at least partially positioned within said fastener cavities; a layer positioned relative to said deck; and a sled (130, 230) movable between an unfired position and a fired position during a firing stroke of the firing member (140, 240), wherein said sled (130, 230) is configured to lift said fasteners toward the anvil during said firing stroke, wherein said sled (130, 230) is releasably engaged with said layer when said sled (130, 230) is in said unfired position, characterised in that said sled (130, 230) comprises a first configuration and a second configuration, wherein said sled (130, 230) is configured to hold the firing member (140, 240) out of engagement with the firing lockout when said sled (130, 230) is in said first configuration thereby allowing the movement of the firing member (140, 240) towards the distal end of said fastener cartridge, wherein said sled (130, 230) is unable to hold the firing member (140, 240) out of engagement with the firing lockout when said sled (130, 230) is in said second configuration thereby preventing the movement of the firing member (140, 240) towards the distal end of said fastener cartridge (110, 210), and wherein said sled (130, 230) is configured to enter into said second configuration if said layer is pulled away from said deck prior to said firing stroke.