This high quality sliding hook allows you to create a ladder that slides along a rail but is hooked on. This allows the ladder to be removable but it can also be stowed vertically as the hook has a upper slider allowing you to push the ladder up against the wall when not in use.
Begin to build your hook over ladder kit with x2 of these (sold as singles) to allow you to create a sliding ladder for your bookcase, kitchen or wine store.
These rollers should be used together with the rubber feet that go at the bottom of the ladder.