PB Cohen Creations

A cotter pin is a metal fastener with two tines that are bent to hold things. The device is commonly called a split pin in the UK. Wikipedia has a pretty good description of how they're commonly used. They come in all different sizes, and are useful to jewelers for providing tension. This photo (click for a bigger image) shows how I used them to make sure two strips of metal were held tightly in place while I "sweat" soldered them together.

Actually, this was just a photo shoot: the placement of the pins during actual use was probably more uniform. First I melted solder to the top strip with the pierced triangles in it, then I placed it over the plain strip, added the cotter pins, and heated the "sandwich" up again until the solder flowed. The "free" pins at the bottom of the photo show what happens after use: the one on the left is unused, the one on the right has been used a few times, probably at least three.

You can see that heating these things up in a torch makes them lose some of their tension/strength, but depending on how thick your bits of metal are, you can use them a few times. These were the smallest stainless steel pins I could find at the hardware store, and were 11 cents each.