Check it out on google - if your boat is 70 feet up in the air and the next part of the canal is 70 feet down, this contraption is what you need to get it down there. Replaces the old rising lock system. Ingenious design (Scottish of course) means that power used is equivalent of boiling 3 kettles full of water - to move one narrow boat and water tank filled with thousands of gallons of water down, while simultaneously moving another narrow boat and water tank up!