simple kerfmaker: how can I improve?

I can't get a kerfmaker, because Bridge City Tools is currently not making them. I came up with the extremely simple alternative below, consisting of just a block of wood and a screw. The screw sticks out from the block by 1/2 '', exactly the width of the router bit. The only tricky part of using this is actually adjusting the screw. I had to turn it slightly one way and then another to get it just right.

Any suggestions on improvement? It would be nice to have a method to adjust the screw rather than trial and error.

This video is a little long winded but it looks like a pretty useful jig. I'd just skip to where he's using it as it's pretty obvious how to make once you see it in action.