Here is a guide that can be used with a router or also as a guide on a drill press.
Step 1: Router Guide
I built this guide for my router years ago. I wanted a quick way to guide the router across hollow core doors so I could stuff wires inside. The guide is very simple, a very thin strip of plywood for a base and a thicker strip for the guide. Glue and tack together and you are done. The router can cut the base plywood the first time you use it.
Step 2: Drill Press Guide
So if I'm doing a project with exposed screws I like to put them in a straight line and have them evenly spaced. So with the router guide clamped to the drill press table it would be easy to keep the holes an even distance from the edge. Then I put Sharpie marks on the fixture for the first and last holes. I also put marks to space the holes 12 inches apart. ( You can see those marks in the cover photo. )
See also a corner fixture:
Step 3: Adding Tape Measures
The 12 inch spacing was fine for the long strips I was drilling. But when I started the shorter strips I wanted shorter spaces, but still even. So I remembered some stick on tape measures I had found at a fabric shop. So I cut two strips so the numbers would get bigger from the center out. This made quick work of putting one hole in the center of two previous holes.
Here are some sources:
Hope you find this simple fixture fun to build and use. I sure did.
Be safe out there. Carl.