I just got another fake Discover Platinum card in the mail today and instead of throwing it out I'm gonna duct tape it to the bottom my tool pouch. I use it as a template for cut-in boxes. You can see right through it to see your mark on the wall, and it's design marks the middle so you just have to trace around it. Tape it to your bucket or pouch with a foot of duct tape. You can then use it to cover the hole in the door jamb where door latches and use the duct tape for cleaning out the filings in the panel you just hole-sawed (especially good for stainless).
When it comes to direct mail freebies, I've taken to keeping a few AOL V9284 CD's to use as "droppable" mirrors for in-wall inspections. If they get scratched? Throw 'em away.
