Simple drill guide for dewalt DCD958 drill or other hand drills with 48.5mm collar. There is clamp test.stl file that you can print to test the fit of the clamp to the drill before you print the actual clamp that takes much longer to print.
The tool consists of two parts - clam that attaches to the drill and guide that slides on two rods. It allows for making square holes and tapping. The it doesn't work that well for setting the position of the hole as the drill chuck and the tool are quite loose and the drill will walk from the initial position.
The tool works well for making square (90 degrees to the surface) holes and tapping existing holes.
You need 5/16 round rod for the guides. I got 36" rod from home improvement store here in California, something like this: 5/16 in. x 36 in. Zinc-Plated Round Rod. Cut two 20cm ~7.5in long pieces.
The clamp is friction fit on the drill. If you have other drill it might not work as is. You can modify the design in Fusion 360: Dewalt DCD985 Drill Guide
The guide plate first the rods tightly. I used the drill to spin the rod while pressing it inside the hole.
The guide clamp should slide the rods with little friction. If this is too tight use 5/16 drill bit to widen the holes. I did that by spinning the drill bit in reverse and pushing it inside the hole, then spin it forward to clear the excess material. Driving the drill in forward from the start will damage the walls and likely misalign the hole.