A stitcher for binding variable thickness collations including a means for determining the thickness of a multi-sheet collation, a stitch head operative to drive a stitch through the multi-sheet collation, an anvil operative to clinch the stitch to bind the sheets of the collation and a plurality of actuators operative to displace forming elements of the stitch head to form the stitch, position the stitch head and anvil against opposite surfaces of the multi-sheet collation, drive the stitch through the collation and clinch the ends of the stitch. A processor, responsive to the thickness value signal, controls the actuators to form the stitch and bind the collation.