I fear the simple explanation belies the complexity of the operation. What Giu has diagrammed is simply an anchor resetting device; one that aids the primary anchor resetting on the change of the tide. I, like many others, think that either a single anchor well set or a Bahama moor would be superior to the method shown, certainly in terms of ease of use and lack of fouling.
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.