This is a late-to-my-game entry. I discovered it in transcribing DVR recordings to DVD and it may have been in other episodes which I haven't found yet.
There is a spring loaded pointy shaft (you can see the striking end protruding upper left) that will leave a screw locating indentation in your material when the shaft is struck.
The bevel end (lower right) is placed in the countersink of a hinge, which automatically centers the tool and therefore the location of the hole to be drilled later. Then, with a hammer or mallet, the shaft is struck and voila! you have a perfectly located hole for the mounting screw. It's a handy tool.
Appearances: Episodes 801, 0107, 1602
Last updated: 7 May 2007