Anti-buckling actuator

A clamping mechanism for a surgical instrument and related methods are disclosed. Upper and lower elongated members are configured to engage each other at a first interlock and a second interlock, the first interlock distal of the second interlock. The clamping mechanism is movable between a first configuration, a second configuration, and a third configuration. In the first configuration, the elongated members are approximated towards each other and the first and second interlocks are not engaged. In the second configuration, the distal portion of the elongated members are moved away from each other, the first interlock is engaged, and the second interlock is not engaged. In the third configuration, the distal portions of the elongated members are moved away from each other relatively, the proximal portions of the elongated members are moved away from each other relatively, the first interlock is engaged, and the second interlock is engaged.