A Tale of Two Capos

A capo is a device used to shorten the effective length of the strings on a guitar (or other stringed instrument). My son has a couple. One is fairly straight forward: it operates like a spring clamp:

The other is three bars of metal linked together with no springs. When I picked it up the first time I thought it was broken. It was not readily apparent how it works.

Even when I put it in the clamping configuration it didn't make sense. What is holding the pieces in place?

Turns out it is the rubber tip on the end of the screw pushing sideways on the curved piece that goes against the back of the neck. Very clever, Mr. Shubb.

Update January 2017 replaced missing pictures.