A surgical fastener applying apparatus comprising: an anvil half-section including a distal anvil portion and a proximal handle portion; a cartridge-receiving half-section including an elongated channel member, the cartridge-receiving half-section including a pair of opposed openings defined through sidewalls of the elongated channel member; a clamping lever secured to the cartridge receiving half-section, the clamping lever having a proximal end and a distal end and including a handle portion; and a disposable assembly including a single use loading unit and a single use firing unit, the disposable assembly configured to be releasably supported within the cartridge-receiving half-section and including a stationary housing for supporting the firing unit, the stationary housing including a distal extension extending therefrom for supporting the single use loading unit, wherein distal extension 504 of firing unit 500 further includes a longitudinal ridge formed on an upper surface thereof that is received within cartridge body of the single use loading unit, wherein said longitudinal ridge provides a bearing surface for a knife supporting member which is secured to a bottom edge of a knife, and wherein the stationary housing includes a pair of flared tabs extending outwardly therefrom, the flared tabs being configured to be releasably received within the opposed openings of the cartridge-receiving half-section to releasably engage the disposable assembly within the cartridge-receiving half-section; the clamping lever being operably associated with the anvil half-section and the cartridge-receiving half-section and being movable from an unclamped position to a clamped position to releasably secure the anvil portion of the anvil half-section in close approximation with the single use loading unit. an anvil half-section including a distal anvil portion and a proximal handle portion; a cartridge-receiving half-section including an elongated channel member, the cartridge-receiving half-section including a pair of opposed openings defined through sidewalls of the elongated channel member; a clamping lever secured to the cartridge receiving half-section, the clamping lever having a proximal end and a distal end and including a handle portion; and a disposable assembly including a single use loading unit and a single use firing unit, the disposable assembly configured to be releasably supported within the cartridge-receiving half-section and including a stationary housing for supporting the firing unit, the stationary housing including a distal extension extending therefrom for supporting the single use loading unit, wherein distal extension 504 of firing unit 500 further includes a longitudinal ridge formed on an upper surface thereof that is received within cartridge body of the single use loading unit, wherein said longitudinal ridge provides a bearing surface for a knife supporting member which is secured to a bottom edge of a knife, and wherein the stationary housing includes a pair of flared tabs extending outwardly therefrom, the flared tabs being configured to be releasably received within the opposed openings of the cartridge-receiving half-section to releasably engage the disposable assembly within the cartridge-receiving half-section; the clamping lever being operably associated with the anvil half-section and the cartridge-receiving half-section and being movable from an unclamped position to a clamped position to releasably secure the anvil portion of the anvil half-section in close approximation with the single use loading unit.