A surgical instrument comprising a handle portion (110), an elongated portion defining a longitudinal axis and extending distally from the handle portion, and first (130) and second jaw members (160) dimensioned to clamp tissue therebetween. The first jaw member has at least one row of fasteners arranged in a row substantially transverse to the longitudinal axis. A pin (154) is disposed in mechanical cooperation with the first jaw member and is movable between a first position where the engagement section is spaced from the second jaw member and a second position where the engagement section engages the second jaw member. The pin has a non-circular cross-section.
