How to Operate Double Canal Locks

Learning how to operate double canal locks can feel daunting the first time you meet one, especially if you are used to narrow locks. The good news is that the basic principles are the same. Take your time, communicate clearly, and keep safety at the centre of every movement.

This guide explains how double canal locks work, how to use them when travelling uphill or downhill, and what to do when sharing with another boat. It is written for narrowboat crews, first-time hirers and solo boaters who want a calm, practical approach.

What Is a Double Canal Lock?

A double canal lock is usually a broad lock chamber that can take two narrowboats side by side, or one wider craft where permitted. You will find them on many broad canals and navigations across the UK.

The chamber is wider than a narrow lock, which means there is more water moving when paddles are opened. This can create extra turbulence, so boat positioning and paddle control matter.

In this article, a double lock means a broad lock chamber, not a staircase lock. Staircase locks have multiple chambers connected directly together and need different handling, so always follow local instructions where they are displayed.

Key Parts of the Lock

Before operating any lock, it helps to understand the main parts. You do not need to know every technical detail, but recognising these features will make the process easier.

• Gates: The large timber or metal doors at each end of the lock.
• Paddles: The mechanisms that let water in or out of the chamber.
• Windlass: The removable handle used to raise and lower many paddles.
• Cill: A ledge below the upper gates. It is a major hazard when travelling downhill.
• Lock landing: A short mooring area before the lock where crew can get on or off safely.
• Balance beams: Long beams used to push lock gates open and closed.

Before You Start

Good preparation prevents most lock problems. Before you reach the lock, slow down and decide who is doing what. If you have crew, agree who will handle the boat and who will work the lock.

Have your windlass ready, but do not put it on the paddle gear until you are ready to use it. A windlass left on a spindle can spin dangerously if the paddle slips.

Check the lock area for signs, instructions or unusual water movement. Some locks have specific rules, especially near rivers, weirs, tidal sections or busy junctions.

• Approach slowly and under control.
• Use the lock landing rather than tying up on bollards meant for waiting boats if signs say not to.
• Keep children and dogs away from the lock edge.
• Do not jump across open gates or gaps.
• Never wrap a rope around your hand.
• Do not tie the boat hard to a bollard while it is rising or falling.

Safety Rules for Double Locks

Double locks can be more powerful than narrow locks because more water is moving through a larger chamber. The safest method is slow and steady.

Open paddles gradually, especially at the start. If the boat begins to surge, hit the side, pull strongly on a rope, or move where you do not want it, close the paddle and reassess.

When descending, always keep the boat forward of the cill. Most locks have a painted cill marker on the lock wall. The stern must not drift back over the cill as the water falls, because the boat can hang up and take on water.

When ascending, watch for water entering through gate paddles. These can be forceful in some locks. If in doubt, start with ground paddles where available and open everything slowly.

How to Operate Double Canal Locks Going Uphill

When travelling uphill, you enter the lock from the lower level and fill the chamber to raise the boat. The lock needs to be empty, or close to empty, before you can enter.

1. Prepare the Lock

Moor at the lock landing and send a crew member to check the lock. If the lock is already empty and the lower gates are open, you can prepare to enter. If it is full, close any open upper gates and paddles, then empty the lock by opening the lower paddles.

Only open gates when the water level inside the lock matches the pound you are on. Forcing gates wastes effort and may damage the structure.

2. Enter the Chamber Slowly

Open the lower gates fully. Bring the boat in gently and stop well clear of the upper gates. In a double lock, a single narrowboat will normally sit to one side rather than in the centre.

If you are sharing with another narrowboat, both boats should enter slowly and settle side by side. Avoid racing into the chamber. A calm entry gives both helms time to adjust.

3. Close the Lower Gates

Once the boat or boats are fully inside, close the lower gates. Check that no ropes, fenders or other items are caught.

The helm should keep the boat under control. A centre line can help, but it should be held, not tied tight. As the boat rises, the rope will need to be adjusted.

4. Fill the Lock Gradually

Open the upper paddles slowly. In a broad chamber, start with one paddle and watch how the water affects the boat. If everything remains settled, open the paddle further and then use the other paddle as needed.

On some locks, opening a paddle on one side can push a single boat across the chamber. If this happens, slow down or close the paddle. The aim is not to fill the lock as quickly as possible, but to fill it safely.

Keep an eye on the bow and stern. The boat may move forward, backwards or sideways as water enters. The helm should use gentle engine movements only if needed.

5. Open the Upper Gates and Leave

When the water level inside the lock matches the upper pound, the upper gates should open easily. If they do not, check that all lower paddles are fully closed and give the water a moment to equalise.

Open the gates, move out slowly, then close the gates and paddles behind you unless a boat is waiting to enter or local signs say otherwise.

How to Operate Double Canal Locks Going Downhill

When travelling downhill, you enter from the upper level and empty the chamber to lower the boat. This is the direction where the cill needs the most attention.

1. Set the Lock

The lock needs to be full before you can enter from above. If it is empty, close the lower gates and paddles, then open the upper paddles to fill it. When levels match, open the upper gates.

2. Enter and Position the Boat

Move into the lock slowly. Keep the boat forward in the chamber, away from the cill at the top gate end. The stern should remain in front of the cill marker as the water drops.

If you are sharing, agree who will enter first and avoid pushing each other about with prop wash. Once inside, keep both boats settled and parallel where possible.

3. Close the Upper Gates

Close the top gates behind the boat. Before opening any paddles, check that the boat is clear of the cill and that ropes are free to run.

If using a rope, keep it loose enough to allow the boat to descend. A tight rope can hang the boat up as the water level falls.

4. Empty the Lock Slowly

Open the lower paddles gradually. The boat will usually drift or pull slightly as water leaves the chamber. The helm should remain alert and adjust gently.

Watch the cill marker throughout the descent. If the stern moves too far back, close the paddles and move the boat forward before continuing.

5. Leave the Lock

When the water level matches the lower pound, open the lower gates. Take care when leaving, as bywashes or cross currents can affect the bow.

Once clear, close the gates and paddles unless another boat is approaching and it is helpful to leave the gates ready for them.

Sharing a Double Lock With Another Boat

Sharing is common in double locks and it saves water. It can also be sociable and efficient, provided both crews communicate.

Before entering, agree the order and who will work which paddles. If one crew is inexperienced, a few calm words before starting can make the whole process smoother.

• Enter the chamber slowly, one boat at a time if space is tight.
• Keep boats parallel and avoid sudden bursts of throttle.
• Open paddles gradually until both helms are comfortable.
• Do not assume the other crew knows your plan.
• Thank the other crew and leave the lock area tidy.

Boats do not usually need to be tied together in a broad lock. In many cases, separate control is safer. If crews choose to use lines between boats, they should be loose, carefully managed and released promptly if needed.

Tips for Solo Boaters

Operating double locks alone is possible, but it needs patience. Give yourself extra time and do not let waiting boats rush you.

Plan each movement before you make it. Use the lock landing, secure the boat sensibly, then set the lock. Keep your windlass with you and avoid unnecessary trips across wet or uneven surfaces.

• Use a centre line to control the boat from the lock side, but never tie it fast while levels change.
• Open paddles in small stages and return to the boat if you are unsure.
• Keep the boat well forward when descending.
• Close paddles fully before moving on to gates.
• Wait for help if conditions feel unsafe, especially in strong wind or fast flows.

If another boat arrives, sharing may make the job easier. It is fine to explain that you are single-handed and to ask how they would like to work the lock together.

Common Mistakes to Avoid

Most lock problems come from rushing or assuming the lock will behave like the last one. Each lock can feel different, even on the same canal.

• Opening paddles too quickly: This can throw the boat about, especially in broad chambers.
• Forgetting the cill: This is one of the most serious downhill hazards.
• Leaving paddles up: Always check paddles are down before leaving unless another crew is taking over immediately.
• Tying ropes tight: Water levels change, and a tight rope can become dangerous.
• Standing in unsafe places: Wet lock sides, balance beams and gate edges can be slippery.
• Poor communication: Make sure everyone knows when paddles are being opened or gates are being moved.

Lock Etiquette

Good lock etiquette keeps the waterways pleasant and efficient. If a boat is coming the other way and the lock is already set in their favour, it is usually courteous to let them use it first.

Help other crews if you can, but always ask before operating paddles or gates for someone else. The helm may have a reason for wanting things done in a particular order.

Close gates and paddles after use unless there is a local instruction, or another boat is clearly ready to enter. Some waterways have specific rules about leaving gates open, so follow posted signs.

Frequently Asked Questions

Are double canal locks harder than narrow locks?

They are not necessarily harder, but they can be more turbulent because the chamber is wider and holds more water. Open paddles slowly, keep the boat under control and take your time.

Can one narrowboat use a double lock on its own?

Yes. A single narrowboat can use a double lock. Position the boat sensibly, usually to one side, and be aware that water movement may push it across the chamber.

Should I open both paddles at the same time?

Not at first. Start with one paddle and see how the boat reacts. If everything is calm, you can open the other paddle gradually. Safety is more important than speed.

What should I do if the boat gets caught or feels wrong?

Close the paddles immediately to stop the water movement. Check ropes, the cill, gates and the boat position. Only continue when the boat is free and under control.

Do I need a crew member on the boat and one on the lock?

It is often easiest with one person steering and one working the lock, but solo boaters can manage with care. The key is to work slowly and keep the boat secure without tying it tight.

A Calm Approach Works Best

The best way to learn how to operate double canal locks is to understand the sequence, work slowly and pay attention to the boat. Set the lock, move in gently, close gates, use paddles gradually, then leave everything safe for the next boater.

With practice, double locks become a normal part of canal cruising. Treat each one with respect, communicate clearly with your crew, and you will soon find a steady rhythm on broad waterways.