Split Pin

One of the simplest fastening devices ever invented is the paperclip. When you think about it, all it consists of is a straight piece of wire, bent to a particular shape. Great for holding papers together.

Not so great at holding a pin through the centre of a rotating wheel or similar object. Enter the simple Split Pin. Push it through the hole in the shaft. Open up the two ends and bend right back for extra security and bingo!

This one resides on the old lightship which I have blipped before.