A system of locks is crucial to a canal. The locks operate to keep the canal water at an even level; they allow a boat to travel up and down hills with no damage to the goods they are carrying or to the boat itself.

Locks work on the simple principle of gravity: water flows downhill. A lock is like a stone box, set into the canal, with gates at either end. A towboat enters the lock and the gate are shut behind it.

A valve is opened in the gate in front of it, allowing the water in the next lock or section of the canal to flow in.

The boat rises with the water, and eventually the water level in the lock matches the water level in the next lock. Then, the gate of the lock are opened and the towboat continues on to the next section of the canal.