I threw together this jig recently to make bridle joints a little easier and more accurate. I set it up so that I can clamp my rail in and cut a kerf, then I flip it and cut the other side. The feather boards insure that the stock is consistently in the correct spot and makes my fingers happy too. Usually I will build a prototype jig and if the concept works well I will build a permanent one with all the bugs worked out. I have yet to do that for this one though.
I added a picture of a completed joint to give an example to those that haven’t seen one (I have yet to clean up the female side so please disregard the looseness!). The first pic of the joint is an example of the rail tenon coming through the style, the second picture is a dry fit taken looking down on the joint.