Avoid Getting Hung up on the Cill

Photo of a boat that has sunk after being hung up on the cill on the Bath Flight, courtesy of Canal & River Trust.

When going through locks, to prevent your boat getting hung up on the cill, remember to maintain control of the boat and ensure it is kept forward of the top lock gate cill. Warning signs are placed on lock gates and the word 'Cill' and white lines are marked on the walls of the lock. If a boat is not kept in front of this marker it can result in the boat sinking within minutes.

  • If the boat is going downstream make sure the ropes are not too tight to allow the boat to move and if the rudder gets caught on the cill, close the bottom gates and open the top gates to refill the lock.
  • When going upstream and the front of your boat happens to get caught on the top gate, stop the water rising by closing the top gate and open the bottom gate to let the water fall.
  • If there are two boats within the lock chamber ensure there is a safe distance and use ropes around the bollards to the keep the boat still.
  • If the side of the boat is alongside the lock wall, refill the lock it will bring the boat away from the wall.


There is more advice on how to prevent and recover from a lock hang-up in the Boater’s Handbook.

Photo below shows a cill marker on a lock chamber wall, courtesy of Canal & River Trust.

Other Hazards

Boats can also get caught on lock gates or stonework when going up or down a lock.

It’s a good idea to always ensure that your boat is moving freely and get ready to close the paddles you are using and open the paddles at the other end of the lock to correct the situation.

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