Using the built in track of the Mortise Rail allows for some simple stops to be easily used. The big square stop shown here would be made in pairs and installed one on each side of the base plate. This would allow the operator to set left and right motion limits (X-axis) for the Rat. An example of where this would be nice to have would be to consistently cut multiple mortises.

The "L" shaped stop is actually designed to locate the stock, it could be made in pairs as well (why not). In the previous mortise example, one would need to locate one end of the workpiece in order to cut these multiple mortises consistently, this stock stop in conjunction with the X-axis stop would allow this to be done.