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