Fin keel
A relatively short, deep ballast keel bolted or moulded to the hull, separate from the rudder.
A fin keel is a separate appendage: a compact, deep foil carrying the ballast, with the rudder mounted separately on a skeg or as a free-standing spade. It gives less wetted surface, better pointing, and a tighter turning circle than a full keel, which is why almost every production boat since the 1970s has one. Grounding loads concentrate on the keel bolts and the hull around them, so keel-bolt condition and the stub area are standard survey items on an older fin-keel boat.
Many fin-keel models were offered with a shoal-draft or wing-keel option for thin-water cruising grounds.