Puzzle

Walking along Silverknowes we came across this!
Not only did we wonder what it was but who did this and why?
Originally the iron bar curved over and met the broken stub on the left of the picture, and after many years has fallen into disuse, but disuse from what? We could not work out any purpose as the tide does not come in very close and it can have no relation to the many ancient war material whose remains appear every now and again. So what was it for?

Now the question is who grabbed this with both hands and bent it this way? Just what sort of individual would wish to tie a knot in an iron bar? I suspect one of those psychiatric patients, usually referred to as 'artists' may well have been involved. Possibly this was the only place for an exhibition?

Answers please on a postcard, and don't forget the stamp this time!