These shorter locks are often 14ft wide but that introduces a problem elsewhere on the canal system where 7ft is the norm.
When we were in Fenny Stratford we encountered a novel solution to this problem.
Alice is a 56ft narrowboat
Alice Too is a 14ft extension:
On the narrow canals they become a 70 narrowhoat.
On the broad canals they become 56ft long and 14ft wide by unhitching Alice Too and breasting her up with the mother ship.