Thanks–you were correct–I ended up making a couple of these out of some scraps of maple, purpleheart and rosewood (I can’t resist hardwood sometimes) along with some cheap thumb screws from Home Depot. I even purchased a couple of brass strips at the local hardware store for decorative purposes and to protect the wood from the thumb screw over time.
I realize now that the marking gauge itself can even be pretty sloppily constructed as long as it can be tightened enough to prevent any parts from moving. I kind of had an epiphany there realizing that if one can use a “finger gauge” to run straight lines down the board it’s really the reference face on the project and the rigidity of the gauge that matter. But of course I wanted them to look beautiful too…
So I ended up making one with the nail at a ~45ish degree angle (but I made the thumb screw on the top of the gauge) and then decided to make another with the thumb screw on the side of the gauge so that it would not get in the way of my fingers or cause any discomfort (like one of the ones Paul uses).
As far as threading the thumb screw–I watched a few DIY youtube videos and one person went so far as to drill a die into his gauge so that the screw would have a metal seat to screw into. However, I did not do anything like this–I just drilled a hole slightly smaller than the thumbscrew and twisted it in with furniture wax on it to lubricate the hole and establish a threaded hole–works like a charm.