Locking jig serves to replace locking levers for added efficiency when working on bigger wood slabs.
Locking jig is attached to your cross rail. Attach your handle to the locking jig, simply by tightening your handle connection onto the locking jig fork. By turning the locking lever, lock the router cart at desired position and make your pass.
If you are using the same bit, you can mark your locking jig positions on your cross rail and speed up your process.