Operating a Lock

How do locks work?

Locks work, quite simply, by ‘lock’ing off a section of canal or sometimes river which can then be filled or emptied of water. There are two tiers, one on either side of the lock or more if it is a flight of locks. The gates can be opened and the boat can move in, then the water is either emptied or filled depending on the desired destination. A windlass is used to open and close paddles on the lock gates, this is what lets the water in and out or allows the water to stay where it is.

Descending in a lock

If the lock is empty, you must first shut the bottom gates and paddles (of course all the gates and paddles should already be shut) and fill the lock by opening the top paddles. Paddles are usually operated with a windlass, which fits on to the lock paddle gear, it is turned to either open or closed and the paddles with catch, which will stop the gear from spinning, and the paddle from dropping when opening them. When the lock is full you can open the top gates and the boat can enter the lock. Once the boat is in the lock you must shut the gates behind it, it’s easier if you leave the paddles open when doing this. Now shut the paddles, it is important not to just let them drop as this can damage the mechanism. Also you must be careful not to release the catch without control over your windlass as it can spin round dangerously.


Depending on the number of ground crew, the size of the boat and the captains skill and confidence with the boat a line can be thrown from the deck to the ground crew. The boat can be held or tied loosely to the locks mooring rings. Correct positioning of the boat and the way in which it is held there is essential. You must not position the boat over the cill line; this is a large concrete ledge partway down the lock beneath the surface of the water. So of course if your boat is lowered down over the position of the cill it will become wedged there. Tying your ropes is very much not advised, think about it, the water level and boat are going down; you don’t want it to be left hanging from the sides of the lock. Common practice is to have someone stood holding the boat, letting more rope through as appropriate. This is not always possible however so another option is to loop the rope round a mooring hoop and throw it back to the captain for him to control. You must then open the paddles on the lower gate; this lets the water out of the lock and into the canal below. When the boat has fully descended and the water is level you can open the gates, return any ropes to the deck and maneuver the boat out of the lock. The captain will then moor the boat at an appropriate space after the lock, ground crew must then close the lock gates and paddles and return to the boats moored position ready to re-board the boat.

Ascending in a lock

Ascending is very similar, just a few different things to remember. We’ll go through the entire process anyway. If a boat has ascended before you the lock will still be full and the top gates may be open, these need to be closed, then the lock needs to be emptied, not forgetting to close the top gate paddles of course! The boat can then move into the lock and the gates close behind, if there is nowhere within the lock to loop a rope around, the captain can either throw a rope ashore or if he has enough skill and confidence simply sit there, maneuvering the boat appropriately.

When ascending it is OK to tie off the rope but obviously as the boat rises the rope will become slack so keep an eye on it and perhaps tighten it up every so often. It would be silly to maneuver the boat to the front of the lock because the paddles are about to open, you don’t want canal water all over your bow and foredeck. Open the top gate paddles, carefully, a sudden rush of water can thrash the boat around within the lock and could quite easily cause a lot of damage especially with an inexperienced captain at the helm. The boat will then rise with the water level within the lock. When the water level in the lock is the same of that of the canal at the top of the lock you will be able to push open the gates, maneuver the boat out and close the gates and paddles behind it. The captain will then moor up at an appropriate and safe place for the ground crew to re-board the boat.



Great care must be taken when using locks especially when concerning children. Heavily thrashing underwater currents are present within the lock. Great heights and unsanitary water are also an issue. So obviously stay dry. The boats themselves can way tens of tonnes so don’t underestimate their force. Life jackets are a sensible option. Having said all this, I myself have spent the best part of my life on boats, operating locks from a very young age and have had not a single scary situation. Perhaps this is my fathers influence but I do not see locks as dangerous or hazardous things at all.