I wanted their name on the front, to identify their backpack, with the phone number on the back. But when you stamp into washers, it raises up the other side, so I couldn't just stamp on the back because it would raise through to the front (see what I mean, in the picture below). I came up with the idea of using 2 washers glued together. You need a glue that will adhere to metal - I went with Gorilla Glue.
After the 5 minutes, you put the objects together like you want them and clamp it tight. I left it several hours in the clamp.TOOL I love), and tucked in the raw ends. I poked it through the washers and sewed it down. Then made a loop of the other end and sewed it down. I slid a carabiner or clip into the loop and that was it. In the picture, boy one is right-side up and girl one is back-side up:
and entering the DIY contest