A surgical instrument is provided that includes a first jaw having a first jaw axis and that includes a proximal portion pivotally mounted to the base to be pivotable about a pivot axis between an open and a closed positions and including a distal portion; a second jaw having a second jaw axis and including a proximal portion secured to the base and including a distal portion; a first side edge secured to the first jaw a second side edge secured to the second jaw; a third side edge secured to the first jaw; a drive member including a cross-beam, which is sized to slideably engage the first, second and third side edges, a first transverse beam portion, and a second transverse beam portion; and a lead screw configured to advance the drive member in a distal direction parallel to the second jaw axis while engaging one or the other of the first and second side edges and the second side edge.