Many moorings (including all those rented out by Chichester Harbour Conservancy) have very heavy riser chains supported by a large buoy to which a lighter chain pennant is attached to secure the boat. It would be impossible to raise the main flotation buoy onto the deck as they are around .65m diameter, and may be supporting as much as 100kgs or more of chain at HW.

The problem with this arrangement is in a wind over tide condition, the pennant chain can abrade the hull. One solution is to fit a plastic tube over the pennant chain, while others fit a slightly shorter mooring rope which takes the load, and secure the chain as a safety back up should the rope chafe and part.