Combine the two rollers with the bevel of your tool and you've defined a flat plane. Precision-machined shouders in the jaws hold your tool perpendicular to the axles and parallel to the wheel surfaces. This design virtually ensures a square edge on your tool if your sharpening stone is flat.
Just spin the clamping screw out, slide the slave jaw off the guide posts and you have wide open access to the wheel mounting screwvs. While you're putting it back togeter, you'll notice the deep, square cut Acme thread. lt spins down fast and grips the tool tight.
