These sets of four are used to moor fairly heavy floating objects at each of four corners. Think drill rigs. 9750 kilos works out to over ten tons each.Two shackles serve two purposes. One is switching out the 'rode' without losing poition. The other is double rodes. That's as much of an explanation thatI received to those who have worked in the brine patch. Found this photo when searching for the Admiralty Patent I think it was from a company in the UK. An anchoring fanatic for sure but I drew the line at buying and shipping four of these! ;D

Cheers

Michael