An endoscopic clip applying system as described which contains a venting system and a clip applying support system which prevents closure of the mechanism before firing. Also, the system ensures proper loading of the clips and prevents them from falling out during loading. Further, the system describes an easily manufacturable, positively opening system which has minimized size requirements. Furthermore, a lock-out mechanism is provided so that the mechanism may not be inadvertently fired. The shaft resists excessive torque as well as holds the clip in place during firing. There are provisions for sealant and non back-up of the clips, as well as features which make the clip properly placed for closure.