Safe sailing through the lock - Rules and Tips

8 minute reading time
Veilig varen door de sluis - Regels en Tips
Sailing through the lock? Not really your hobby? Many water sports enthusiasts sweat when they see a lock approaching. However, if you are going to sail in the Netherlands, you will undoubtedly come across a lot of locks. Especially if you are not a fan of mooring in a lock, I am happy to help you by means of a number of tips. If you follow this, sailing through the lock will no longer be an obstacle. Do you actually know why locks are necessary?

What is a lock

A lock is indispensable for the proper functioning of a canal. The water level is maintained by means of 1 or 2 lock gates. But what about the passing shipping traffic? The second function of a lock has everything to do with this. The passing boats are taken to a higher or lower level by means of the lock.


These locks always work in the same order.

  • Sluice gates open. Ships can now enter.
  • The lock gates close behind the ship.
  • The bulkheads open.
  • Due to the difference in pressure on the different sides of the lock gates, the water now flows out or into the lock.
  • Water level right? Doors open and the ship can sail out again.


A smart system, those locks. They have everything to do with the principle of communicating vessels. How did all this actually start? Point by point a number of important moments in the history of the lock.

  • The dam was the first simple form of a flood defence.
  • Dams were built early in human history. Mainly to raise the water level of the rivers.
  • Several weirs were needed to reach the target, so not very practical for the ships.
  • Then came the so-called flash lock. The ship was placed in front of the dam, a small door opened and the ship floated on the torrent of water.
  • Upstream, however, was more difficult. Then of course the above didn't work. In that case, ropes were used to lift the ship. This method is not really without danger and risk, so time for innovation.
  • The lock was born. This could be opened with the same amount of water on both sides. This prevented the enormous deluge that caused quite a bit of danger.
  • This lock first entered Europe in 1373.
  • Later still, the doors change, they become more pointed. The locks are also getting bigger and more automated.

How does a lock work

I already mentioned to you the law of the communicating vessels. Very interesting by the way! What does this principle mean? In two connected vessels, the liquid level is always the same. It makes no difference how big the vessels are or what shape they have. Of course, there must be equal air pressure.

If one of the barrels is sealed airtight, something changes. An upper or lower pressure is created and the balance changes. At top pressure, the water level in this vessel drops and at underpressure it will rise. The balance must be restored! This moves until the same pressure is present in both vessels again.

How does this pressure arise? By gravity! How do we apply this to the lock? The barrels represent a part of the canal and the lock. The amount of water does not matter. The difference in height of the water. I make it concrete for you:

You sail with your ship in the direction of a lock. You want to go to a part of the canal that is higher up. You enter the lock and the doors close. The water flows in when the baffles are open.

There is a height difference. The part of the water that is higher than the water level in the lock exerts pressure on the underlying parts of water. Now the water is rising in the lock. Just until it is the same level as the water in the canal. The lock gates open and you continue your cruise.

Enter the lock; tips

  • Look for information in the almanac or pilot book.
    This is not the case with all locks. Sometimes, however, you can read useful information about times and other guidelines, among other things.
  • Think in advance whether you want to moor on the low or the high shore.
    If you choose the low one, you will automatically float against the wall when you moor. If attaching the lines does not go well in one go, that is no problem. If you take the high shore, you can sail away a little easier. It may of course happen that your preferred side is not possible. It is too busy or the lock master indicates otherwise. The lines must therefore be ready for use on both sides.
  • Hang fenders in advance
    If you have no idea which lock wall you will encounter, hang them on both sides.
  • Commercial shipping has priority
    Before entering the lock, wait until these ships are stationary, moored and have turned off the propeller. If the propeller is still turning and you end up in the propeller water, the boat will be difficult to steer. Sometimes, however, the lock keeper chooses a different order. Keep an eye on this.
  • Enter the lock in order of arrival
    Always sail as far forward as possible. Again, pay attention to the instructions of the lock keeper.
  • Connect well
    Enter the lock at a reasonable speed. It is annoying when yachts behind you have to wait unnecessarily. You still have enough time to brake in the lock itself.
  • Secure the ship both front and rear
    Be careful not to put the lines too tight. Otherwise it will be difficult for you to bounce along with the rising and falling water. Run the line over the lock wall. Bring him back on deck. Hold the end of the line. So you can put it on or let it celebrate. The boat can easily keep up with the water level.
  • screw out
  • Listen to the VHF radio if necessary
    Follow directions from the lock master.
  • Professional shipping also comes first when sailing out

Sailing out of the lock

  • The front boats leave first
    Also give these boats plenty of space to do this.
  • Sailing away from the high shore
    This is very easy. You naturally blow off the lock wall, as it were. First loosen the front line. Then let the bow blow away. Until you have enough room to sail away. Now release the rear line and you can choose the open sea.
  • Sailing away from low shore
    Pull the stern towards the wall by hand. Use the back line for this. In this way the bow is released sufficiently to be able to sail away.

All tips briefly and concisely at a glance? It is useful to watch the following short video for this. Recommended!

Mooring in the lock with a sailboat

A few tips for the sailors among us:

  • Agree what everyone's job is
    The skipper gives everyone their own task. To be safe, hang the fenders on the starboard and port side.
  • bow in the wind
    Very nice, because now you can safely enter the lock. Hold the engine in forward a little bit. This keeps the propeller pushing water against the rudder. The boat can then be steered well, even at a minimum speed. First throw the hinterland rope around a bollard. Continue a little further. Now the front mooring line to a bollard.
  • For the wind with the wind from behind
    This requires a little more helmsmanship. Make sure that the boat does not go in too fast. The hinterland is now very important. Have someone ready and try this mooring line at the right time to throw the bollard. This allows the boat to be braked slightly.

Traffic lights at the lock

  • Red light: Just like on the road, this means waiting.
  • Red/green: the lock is about to open. You can get ready to enter the lock.
  • Green: access to the lock is free.

Locks and security

If you follow the rules, then nothing will happen. However, a lock is not entirely without danger. A few points of attention:

  • Look where the lifebuoy hangs in the lock.
  • Automatic locks usually have an emergency button.
  • If someone falls into the lock, use this button immediately.
  • Make sure children stay in a safe place.
  • Put on a life jacket for young children.

Passing a bridge

Broadly speaking, the same rules apply to a bridge as to a lock. Some comments:

  • Pay attention to the light signals.
  • Your vertical clearance determines whether the bridge should open. A little before the bridge you will usually read a gauge with the exact vertical clearance.
  • You will see lamps above the fairway of the bridge. If the lamp is yellow, you may pass under the closed bridge. Watch out for any oncoming traffic.
  • If both lamps are yellow, you can be sure that there are no oncoming traffic.
  • If the lights are double red, the bridge is not operated at that time.
  • Stay close to the bridge, because most of the time cameras are used and the bridge is controlled remotely.
  • Optionally, you can call the bridge via the VHF radio. Usually you use channel 18 for this.
  • Red with green light: the control is coming. Get ready and drive slowly towards the bridge.
  • Wait until the bridge is fully open before continuing. The top lamp is then off and the bottom one glows green.

You will see, the more times you have sailed through the lock, the easier it is. Does the boat cover still need cleaning? Has he been impregnated this year? Make it easy on yourself and request my free e-book with a step-by-step plan for boat cover cleaning & impregnation.