Here's an idea that everybody else must have already discovered, but just
occured to me this afternoon.

I set up the fuel line for my new Webasto furnace this afternoon.I needed to
drill holes in a piece of sheet metal stock. The metal box containing the fuel
pump had four very short studs protruding from the back. The studs were too
short to get a solid bite into anything substantial enough to support the fuel
pump, and pulling them out and putting in longer bolts would have required
partial disassembly of the fuel pump mechanism inside the box. To solve the
problem, I decided to mount the pump box on a small piece of thin sheet metal,
and then screw the sheet metal into place with 1" fasteners. (This allows for
two layers of rubber sound dampeners, one between the box and the metal plate,
and the second between the metal plate and the floorboard in the engine room).

Problem: How to accurately locate the holes that needed to be drilled into the
sheet metal?

Solution: Grabbed a chunk of corrugated cardboard slightly larger than area
defined by the studs on the fuel pump box. Shoved the cardboard down onto the
ends of the studs protruding from the box, resulting in four exactly-located
little dimples. Sat the dimpled cardboard on the sheet metal stock, drilled
through the dimples, and voila'! Perfect the first time. Much better than if I
had tried to measure by hand.