We used to use coffee can lids and discrded tupperware (e.g. lids w/o containers) as squeegees for making surfboards (& other polyester resin things) You can cut `em w/ scissors.

When I'ze a kid, I had no money, so I learned to improvise. It's amazing what you can do with stuff discarded. I now keep boxes of categorized (plastic, aluminum, steel, lead, etc) discards. I pick up lead wheel weights off the ground at service station whenever I see them. A penny with a hole in the center makes a good wheel for those little Brio trains. Always look for opportunities to innovate.

I am building a rack so I can cut all of my lumber over two feet long into strips and store it together. I figure I can build a boat from nothing but leftovers that I already have.

The key is to organize your stuff so you know what you have and where to find it.

Also, hardware stores, and stores like Walmart, Kmart & Target clearance stuff. You can buy their discards if you keep an eye open for things that will be useful later. The problem is all of this adds up to clutter.