Door Butt Gauge
For accuracy and speed when hanging doors from scratch, I use a butt gauge (see drawing) that I made out of 1-in. aluminum angle stock. Bending one leg of the angle over 90° just 1/8 in. down from the top, and cutting slots the same size as the hinges where they are to be positioned on the door, complete the gauge.
To mark the door, just hook the bend over the door edge and scribe the hinge cutouts with a utility knife. For the hinge jamb, hold the unbent face of the top of the gauge to the top of the jamb and mark the butt spacing. When you are not hanging doors, the gauge and a couple of clamps serve as a handy straightedge for cutting and scribing lines on almost anything.
—John Toly, Richmond, CA
Edited and illustrated by Charles Miller
From Fine Homebuilding #8
I have an old Stanley butt gauge. I can't figure out how it works.
By the way; I have a new best friend. It's my wife's old yoga mat. As an old, semi-retired carpenter, I do a lot of punch list work now.
I've found several great uses for it. Makes a great drop cloth for small drywall patches, and painting, of course. While doing punch lists, it's great for setting my tool bags on so I don't scratch the wood, or tile floors. It will grip a piece of wood that needs sanding on my work table. Folded up, it saves my knees, and when I'm done for the day it's great for doing a little yoga!
I don't leave home without it.
rockinroger - Good tip about the yoga mat!
For a Stanley #95 butt gauge, this is a nice one with instructions.
I've used the Butt Marker for hinges with a radius corner before routers. Use a corner chisel for square corners.