Small Whiteboard Eraser

I wanted a small whiteboard eraser and didn't want to go out and buy one. I also had a lot of socks that were missing pairs or had holes. This is the result.

If you don't have a sock, any small piece of foam or fabric that will roll/bunch up to around the same size as the eraser will work. My design is 72mm x 36mm (and 20mm deep), but you can scale this to create a whiteboard eraser of any size and it'll probably still work. Maybe you can make a giant one that holds a T-shirt or something.

Also, If you wanted a magnetic eraser you can glue a magnet inside; the walls are only 2mm thick.