I like to test the batteries I have collected to see whether they still have any life left in them before sending them to be recycled. This can be a tedious process, so I wanted to make part of the process easier.
This battery testing jig uses a foot pedal (doorbell button) to activate a solenoid (powered by 4 AA batteries). This pulls the battery into place between the solenoid and a screw at the other end. This connects the battery to my multimeter, without having to hold a lead in each hand while simultaneously trying to look at the multimeter. I can then sort the batteries according to the results.