There is usually something a little strange about disembodied hands (or arms or legs or other extremities). My husband has a habit of managing to sleep with one arm thrust under his pillow and a hand dangling over my head. Many a time I have been alarmed at the sight or touch of this disembodied hand in the night! Thankfully though I am not disturbed by knockers with hands.
The little hand clutching a ball (or occasionally an apple) is called The hand of Fatima. A symbol of protection, it is a common door knocker in Mediterranean countries but originated in Muslim countries where Fatima was the Prophet’s daughter. This ancient symbol was called Miriam’s hand in the Jewish faith. Sometimes the hand wears a ring or two, sometimes a cuff or bracelet. There are some that are flat and very stylised, hardly recognisable as hands at all.
Other hands on your knockers (sorry, I can’t help myself) include what I think of ‘hand and laurel’ but apparently is actually called “The Wellington”.
Apparently the creation of it has been credited to a London ironmonger called David Bray in 1814, celebrating the Duke of Wellington’s victories in Spain and Portugal. The hand of the “immortal hero” grasps a field Marshall’s baton and a wreath of victory. Until I read about it on Shannon Selin’s wonderful blog post about its history I hadn’t really noted the lion at the base, which apparently represents British valour overpowering tyranny.