Traditional Techniques: NarrowBoat, Summer 2011

David Blagrove

David Blagrove explains the mystery of how to open lock gates with your working boat pair

One of the skills of the working boater was that of ‘thumblining’. It is quite simple really, although it can mystify the lay observer. Lines are attached to the handrail of one or both of the bottom gates of a Grand Union lock, the motor boat holds back and the gates open, then it goes forward and the line flies off without being touched by human hand. The secret lies in two things: one is getting the right amount of line (which is attached to the mast looby) and the other is fixing the slip hitch that makes it all happen. This latter is a very simple device, similar to what dockers called a Blackwall hitch. The tail of the line passes underneath the part that takes the strain so that it tightens as the boat pulls, but once the strain is off it loosens. The amount of line used is such that when the fore ends are against the bottom gates, with the lock empty, there is a slight curve. This gives sufficient slack for the boats to move back from the gates enough for them to …

To read the full article…

…you need to be a subscriber to NarrowBoat. If you are, you can login here. If not, you can buy a subscription here . If you are having trouble logging in, please contact support at

Thumblining featured image