I had a surplus of iPhone and android batteries that weren't new but hadn't dropped below 80% capacity (which is when they really start to give up the ghost), so I figured I'd make some handy pocket flashlights. The slimmer, the better. And with strong neodymium magnets on the back so they can stick to things. I designed a form to hold all the components and that I could make with the tools and materials I had on hand and then got to work.

The leftmost blanks are of the back and the right are of the front.