A Guide to Operating Locks

About canal locks

A lock consists of a lock chamber which is brick, stone or metal and holds the water. To allow boats to get in and out, and to keep the water in, there are gates at each end of the lock.  Sometimes there is one single lock gate, other times there are two double gates, and these are pushed open by balance beams on the gates. 

It is only possible to open a gate when the water levels on both sides are the same. So, the top lock will only open when the lock is full of water, and the bottom gate only opens when the lock is empty or nearly empty.

There are paddles on locks which are raised and lowered to control the water flow and alter the level. The cill is a large raised ledge at the top end of the lock which the top gate shuts against. So, how does a lock work on a canal?

Locks are worked by water pressure and user muscle power!

There are no pumps or electric motors except on some of the larger commercial traffic or guillotine locks.

Narrow locks are wide enough for one boat, but wide locks generally hold two boats side by side.  They are predominantly found in the South or on wide or barge canals.

Windlass - You will require a windlass for winding the canal lock paddle mechanism up and down - this is an L shaped handle which is fitted to the spindle on the paddle. Always wind paddles slowly, checking to see what effect the water is having on your boat. 

Anti-vandal key - You may also require a Waterways Authority key or anti-vandal key to unlock the canal lock paddle mechanism – ask your marina about this when you collect the boat.

Sluices – These are channels in the lock which enable water to pass from one area to another.

Paddle gear – This can either be hydraulic or rack and pinion. On the rack and pinion type there is a safety catch or pawl which stops the gears from slipping down and keeps the paddle raised when the windlass is removed. When you have finished winding paddles check the pawl is in position and then take off the windlass.

Lock landing – This is a section of the towpath either above or below the lock for boats to moor and either wait to enter the lock or let crew off the boat. They can also be pontoons reached by a ladder.

How to operate a canal lock

As we said, the water flow in locks is controlled by the paddles, so to learn how to operate a canal lock, let’s start with a few safety tips:

• Keep a firm grip of the windlass when winding. If this needs adjusting, put the safety catch (pawl) in place and then start again.

• Only use a windlass that fits the spindle snugly – we will supply you with these on the boat.

• Keep fingers, hair and clothing away from the gears.

• Never leave your windlass handle on the paddle gear. Should the safety catch (pawl) disconnect and the paddle drop your windlass handle could spin round and you may either lose it in the canal or it could hit someone. 

• Always wind the paddles back down – if you let them drop, they could break. To release the safety catch (pawl), wind the paddle up a little, take the strain with the windlass, then remove the safety catch (pawl) and wind down the paddle.

When you arrive at a lock, moor up and send at least one of your crew to check whether it's full of water or empty, or if another boat is already using the lock.  If the lock is in use, moor up far enough away to avoid the currents while it is being emptied. 

If the lock is empty of water, open the gates by pushing against the balance beams. Take the boat in steadily then close the gates. 

Try to keep the boat in the middle of the lock to avoid anything catching as the water rises.

If the lock is full of water, moor up below the lock whilst your crew empty the lock by slowly raising the paddles. When the lock is empty, go in.

When the gates are closed, your crew can then move to the far end of the lock and slowly open the top, 'ground' paddles. These are situated either side of the lock, winding up the ground paddles, followed by any centre lock paddles, if fitted, to fill the lock.

Always wind slowly to avoid making a tidal wave in the lock which will throw the boat backwards against the bottom gates. Leave the pawl or safety catch in place whilst raising the paddles. Once the paddles are up and you are happy with the flow and its effect on the boat, remove the windlass from the mechanism.

If you find you need to control the movement of the boat, do it with gentle bursts of throttle - forward if the boat is moving backwards, reverse if the boat is moving forwards.

Your crew must understand the importance of opening the paddles slowly, to prevent the boat moving about too much in the lock.

When the lock is full, open the top gate and steer the boat out of the lock. Whilst you are doing this, your crew will shut the top paddles. They then shut the gate behind the boat while you moor up for them to get back on board. If another boat is coming towards you, your crew should leave the gate open for them.

Again, when you arrive at the lock, moor up and send your crew to check the lock.

If the lock is full, the crew can open the gate and you can steer the boat in.  However, if the lock is empty and no boat is approaching from below, the lock will need to be filled by winding up the paddles nearest to your boat. When the lock is full open the gate and steer in. Close the gate and lower the paddles.

Keep the back of your boat clear of the cill on the top gates. Open the paddles to the  front of the boat to empty the lock. As the lock empties, continue to look behind you to check that the back of the boat is clear of the cill. Use gentle bursts of throttle to keep the boat steady.

When the water levels are equal steer, the boat out of the lock. Close the gates and lower the paddles before you continue your journey unless another boat is coming towards you.

You should always ensure the safety of your boat, yourself, your crew, children, pets and bystanders. These are some points to help:

• Take your time with locks – there is no rush and you are on holiday.

• Children and non-swimmers are recommended to wear life jackets and pets kept under control around locks.

• Ensure that you and your crew are wearing suitable footwear, particularly avoiding high heeled, open-toed shoes and flip-flops. A windlass dropped onto bare toes can be extremely painful!

• Always keep one person on the boat when it is in a lock.

• Secure spectacles, loose hair or clothing and keep scarves tucked in. Avoid wearing anything around the neck such as long necklaces, cameras and shoulder bags which can catch on the windlass or in the paddle mechanism.

• Do not allow small children to touch the mechanisms around the locks and make sure they are supervised at all times.

• Keep children away from the lock edge and watch out for slippery surfaces.

If a Lock keeper is on duty, always follow their instructions. You will usually be expected to operate the locks yourself, but under instruction or supervision. Some locks, particularly on rivers are always operated by Lock-keepers. Most locks, however, are self-operated.

If the water is in your favour, you have right of way; if the water is against you then a boat seen coming towards you has right of way, as they can make use of the water. 

You may have to wait a few minutes for the oncoming boat to get into a position to use the lock - please be patient.

Do not be tempted to use lock moorings for overnight stays or moor there for longer than it takes to lock as you will be obstructing other users.

If a boat is coming towards you as you exit the lock, leave the gates open for them.