I machined the backs of the removable jaw faces on a mini (drill press) vise for wheel clearance and a vertical slot (axle diameter ++) in the same faces so that you can use the vise tightening screw to adjust the wheel gauge IN or OUT. Comes in handy when the insulating insert (e.g.Con-Cor) is not all the way in and you need to get inside this obstruction before pushing out to increase gauge. This also reduces the chance of bending the axle with the needlenose/screwdriver method. you are pushing/pulling nice and square against the wheels.