I recently built a Mechanical counter really just to discover how it actually worked, so with the ‘How it works’ theme in mind this project looks at how a simple lock works. Normally a Mortise lock fitted into a door will have a latch which is opened by turning the door handle and a Deadbolt that can be locked or opened with a key. For the purpose of this project I have removed the latch and use just a single lever to lock the bolt. I have fitted this into the lid of a container so that you finish up with a lockable container for keeping small items secure. In the picture shown the Bolt is Green and the Lever is red, when the key is fitted and turned, it firstly lifts the lever from its locking engagement with the bolt and continued turning then moves the bolt to its lock position. The Cap can now be rotated 30° anti-clockwise and pulled from the container.