A surgical stapling device has an elongated body and a removable loading unit and a securing structure for securing the loading unit onto the elongated body. A guiding ramp guides the movement of the loading unit as it is mounted onto the loading portion. The locking structure has a first position for locking movement of the loading unit and enabling firing rod to engage the loading unit. The locking unit has a second position for allowing the loading unit to be disengaged and removed from the device.