By far the easiest and safest way to get through locks is with crew. Even one other person on the boat makes things quicker and simpler as they can go and wrangle the gates and paddles while you stay aboard and steer (or vice versa).
It is sensible to have a pre-determined system of communication between you, as simple as certain waves and gestures to indicate ‘are you ready?’ and ‘ok, open the sluices’ and so on.
The gist of the procedure is as follows:-
1. The boat pauses briefly at the lock landing (the section of canal just before the lock, usually marked with bollards for temporarily tying the boat while using the lock, if needed) so that a crew member can step off, remembering to take a windlass with them to operate the sluices (a windlass is a metal handle with a hole in one end that fits onto the lock paddle mechanism) Then the boat waits either on the landing or in the middle of the canal, until the lock is ready.
2. The crew member that stepped ashore walks up to the lock to see if it’s empty or full (and either fill or empty it as required). in other words, if you’re trying to bring the boat up, you need to start with the lock empty. If you’re going down, the lock should be full.
3. Always check to see if another boat is coming that could use the lock in its current state before you start changing it. For example, if you need to empty the lock but there’s a boat coming that wants to go down, that boat might as well be in the lock while you empty it (instead of waiting while you empty the lock, bring your boat in then fill it again). You will appreciate the same courtesy by other boaters for you.
4. Emptying the lock is done by winding open both paddles at the end of the lock where the canal is lower; filling it is done by opening both paddles at the end where the canal is higher. In both cases it is essential that you check that the other set of paddles is fully closed, otherwise water will just run straight through the lock from high to low; your lock won’t get set but the higher lock pound might run dry.
5. When the lock is set, you’ll be able to open the gate(s) at whichever end of the lock your boat is waiting at. On narrow locks, there are typically two gates at the low end and just a single gate at the top.
On wide locks there will be two gates at either end; if you’re confident about steering, you can get away with opening just one but if you mess up your steering, you may hit the other one and cause damage, which the Canal & River Trust unsurprisingly takes a dim view of. It’s a lot more effort to open and close both but it is the preferable way of doing things.
Of course, if you’re sharing the lock with another boat (which is again preferable as it’s likely that at least one boat will have crew who can sort the paddle gear) then you’d usually need to open both gates anyway, though there are some clever-clogs who will only open one and manoeuvre the second boat across within the lock.
6. The boat can now be steered into the lock. When it is fully inside the chamber, the crew can close the gates behind them.
7. When the person steering the boat is ready (this is where hand signals come into play), the crew can – gently, if going up and letting water in – start to open the sluices by pushing the windlass onto the paddle gear and cranking the handle.
Depending on how deep the lock is, the water pressure can be immense so if you open the paddles too quickly, it will rush in like Niagara Falls and slam the boat back towards the gates. This can cause damage to the gates and your boat, so it’s best just to crack the paddles open a little for the first minute or so, then raise them further (again, with a thumbs-up from the steerer when ready)
8. If your boat is going down, it is absolutely critical that you ensure the stern of the boat, including any rear fender, is in front of the line marked “CILL” in white, usually a foot or two in front of the lower gates. That’s because there’s a huge concrete block hidden in the water that sticks out to where the cill marker is (it’s part of the lock structure, it has to be there) and if your boat catches on that as it goes down, it will tip forwards, potentially flooding the boat and sinking it. This is the most common way that narrowboats sink and in a significant number of cases, it has led to people inside the boat drowning.
Whether you’re going down or up, you’ll also need to keep on the front (bow) fender to make sure it doesn’t catch on any part of the lock gate, as this can also result in the boat tipping (and ultimately, sinking).
In an emergency, ignore good practice and just drop the sluice paddles by releasing the catch though be careful not to have the windlass still on the mechanism as you do, as it will spin round very fast indeed and can easily break your arm while doing so.
For that same reason, never take your hand off the windlass when it’s on the paddle gear; if the ratchets holding the paddle up were to slip (and they do), the windlass will whirr round at tremendous pace and with tremendous force. People have been badly injured by this.
9. Once the lock is empty (if going down) or full (if going up), the water will stop swirling and you’ll find that you can push open the end gates just by leaning on them, usually with your buttocks. If you push and the gate won’t open, you probably need to wait another minute or so – it can take an age for the water pressure on either side of the gates to fully equalise, even if it seems as though nothing more is flowing.
10. The steerer can then bring the boat out of the lock and will pause on the lock landing for the crew.
11. The crew must ensure all the sluice paddles are down and (unless there is another boat approaching that wishes to use the lock from the direction you are heading) shut the gates behind you. Failing to do this is terribly poor etiquette.
 Strangely, not the case on the Macclesfield canal where both top and bottom have dual gates. And on the South Stratford canal you’ll find a single gate at both ends.
 Unless specifically instructed otherwise by a notice on the lock. For example, on the Warwickshire River Avon, the rule is to leave the gates open.