My wife used to wonder why I have all kinds of metal, rubber, plastic, etc stuff tossed in boxes and bin shelves. But after making a few things she needed she got the picture and stopped complaining. A metal ruler is good idea. Didn't think of that and I have a few of those. You forgot the number one thing you have to have on hand- metal coat hangers. Another good thing to stock up on when going to the dollar store are those thick foam beer/coke can holders. Those have better foam than the expensive stuff at the LHS, and also make for padding in a lot of applications. They make great vibration dampers for shop equipment like scroll saws.