This very useful knot was taught to me by the skipper of a superyacht I worked on. Each morning he would show us how to tie a particular knot which we then practised before starting the day’s tasks.
The bowline on a bight is different from a conventional bowline and is used when a dependable loop is required but an end of a rope is not available.
It has some good uses such as providing a toe hold in the middle of a rope or making an emergency bosun’s chair. It can also be used to make an upper rope ‘block’ since it provides two bight loops, so the line can be doubled to reduce or spread the load to be hauled.