Ryeford Double Lock

How a lock operates

By Paul Leonard

Simple Single lock v's Double lock

As you will know, water will only flow downhill. Canal boats have a need to go uphill as well as downhill so the lock was developed to enable canal boats to change levels. The Simple Single lock operates on the basis that water can be taken from the upstream side to raise the water level in the lock. Double locks share a gate i.e the bottom gate for the Upper lock is the top gate for the Bottom lock. Double staircase locks need to change levels twice so there needs to be enough water in the Upper lock to raise the level in the Bottom lock. This water will be lost as a barge is let down to the lower level. If the next boat is travelling  upstream the Bottom lock will need to be filled from the Upper lock.

Animation designed by Seana Kozar.