Single handed working
WHILST the limitations you describe [Lock closed to single crewed users!} are worthwhile warnings, they are not actually true, writes Mike Todd.
Single handed working can, in general, be undertaken without the use of a ladder (assuming a lock with only one).
Indeed, when we started back in 1967, ladders were a rarity and boat handling with ropes would be the norm. This remains a good way for single handers, albeit perhaps slightly slower.
Uncomfortable at using ladders
When we came down through Etruria a few weeks back, we had to wait at one point whilst a single hander locked through. His style was largely this as he was, so he said, uncomfortable in using ladders. So there are still those who recall this method of operation.
Whilst it may have involved greater wear and tear, notably from careless or inexperienced operation, my understanding is that the traditional way of working closely followed this pattern. The main factor that causes concern with navigation authorities is that, when ascending, the steerer jumps off the stern as it passes just below the lock (there is usually a set of steps for this purpose) allowing the boat to drift in and end up just at the buffer plate (if fitted) The concern is that if not judged correctly the boat will impact the top end with more force and potentially cause, individually or collectively, damage or wear to the structure.
That said, using ropes will obviate this factor and allow single handers to pass a lock without damage to lock, boat or boater.