Luban mortice gauge wheel is designed to hold the setting of the cutters relative to each other while the fence is adjusted independently or vice versa if you want to adjust one rod but leave everything else set. With both cutters set to the same line and the bridle locked, you can use it as a standard marking gauge but with the option for which side you would like the bevel on. The bridle can also be used ahead of the fence to stabilize the bars for cutting marks further in from the edge. In the horizontal position the cutters won’t engage rotate into the vertical position and the thinner wall of the saddle casting lowers the cutter into the work. A very controlled way to lay difficult marks. For a tool that is produced in volume, the cleverness of design, ease of use and overall finish on this gauge is remarkable.