A surgical fastening device, comprising: an elongate shaft; an end effector coupled to a distal end of the elongate shaft, the end effector including a cartridge jaw (1110a, 7048) and an anvil (1110b, 7050) pivotally coupled to one another and movable between an open position and a closed position in which tissue can be engaged therebetween; a cam pin (7010, 7052) disposed within a cam slot formed in a movable cam plate (7026, 7040) of the end effector, the cam pin (7010, 7052) having first, second, and third positions within the cam slot, wherein movement of the cam pin (7010, 7052) within the cam slot between the second and third positions is effective to change a distance between a proximal end of each of the cartridge jaw (1110a, 7048) and the anvil (1110b, 7050); and a staple cartridge (1112, 7012) configured to be removably disposed within a channel formed in the cartridge jaw (11101, 7048) and including a plurality of staples disposed therein; wherein the staple cartridge (1112, 7012) is configured to move the cam plate (7026, 7040) when the staple cartridge (1112, 7012) is fully seated within the cartridge jaw (1110a, 7048) so as to cause the cam pin (7010, 7056) to move out of the first position and into one of the second and third positions; characterized in that the cam plate (7026, 7040) prevents the cam pin (7101, 7056) from moving out of the first position when the staple cartridge (1112, 7012) is not fully seated within the cartridge jaw (1110a, 7048), wherein when the cam pin (7010, 7056) is in the first position at least one of closure of the anvil (1110b, 7050) and cartridge jaw (1110a, 7049) and firing of the staples into tissue engaged between the anvil (1110b, 7050) and the cartridge jaw (1110a, 7048) is prevented. an elongate shaft; an end effector coupled to a distal end of the elongate shaft, the end effector including a cartridge jaw (1110a, 7048) and an anvil (1110b, 7050) pivotally coupled to one another and movable between an open position and a closed position in which tissue can be engaged therebetween; a cam pin (7010, 7052) disposed within a cam slot formed in a movable cam plate (7026, 7040) of the end effector, the cam pin (7010, 7052) having first, second, and third positions within the cam slot, wherein movement of the cam pin (7010, 7052) within the cam slot between the second and third positions is effective to change a distance between a proximal end of each of the cartridge jaw (1110a, 7048) and the anvil (1110b, 7050); and a staple cartridge (1112, 7012) configured to be removably disposed within a channel formed in the cartridge jaw (11101, 7048) and including a plurality of staples disposed therein; wherein the staple cartridge (1112, 7012) is configured to move the cam plate (7026, 7040) when the staple cartridge (1112, 7012) is fully seated within the cartridge jaw (1110a, 7048) so as to cause the cam pin (7010, 7056) to move out of the first position and into one of the second and third positions; characterized in that the cam plate (7026, 7040) prevents the cam pin (7101, 7056) from moving out of the first position when the staple cartridge (1112, 7012) is not fully seated within the cartridge jaw (1110a, 7048), wherein when the cam pin (7010, 7056) is in the first position at least one of closure of the anvil (1110b, 7050) and cartridge jaw (1110a, 7049) and firing of the staples into tissue engaged between the anvil (1110b, 7050) and the cartridge jaw (1110a, 7048) is prevented.