Unlike most of the locks on the English network, the locks on the Lowland canals have no by-pass weirs. As the F&C "flows" from its summit, the locks "run" all the time over the top of the gates due to excess water, this being Scotland after all. On top of that, the lock gates themselves have sluices built in above the water level, which means that boats going downhill can get cascaded with water in the stern when the locks are being filled. Going uphill, you are met with a waterfall coming from way above your head at the bow.
Contrary to a previous post, I'm sure the hire fleet would love to have all the locks self operated by the crews, but these locks are not safe, and I speak as one who has done thousands of locks, big and small, often single handed, but I wouldn't do these on my own.
In fact, despite the generally excellent work performed by both the SC and Re-Union lock teams, flooded boats are not as rare as they should be, and an out of control boat caught in the water stream coming from one of the gate sluices is not a pretty sight. Steel narrowboats are one thing, but a plastic yacht out of control would be another.