Arzúa to Santiago
"These door knockers in the shape of a hand holding a ball are probably the most interesting. The hand emerges from a lacy cuff, often with a bracelet around it, and bears one – sometimes two – rings, although not always on the same finger. They are occasionally made of brass but more often of iron.
The hand and the number five figure significantly in Arabic, and also in Jewish, tradition, and are particularly associated with warding off the evil eye. Fatima Zahra was the daughter of the Prophet Mohammed. Hence, the occupants of a house with a door knocker in that shape were protected against evil. Originally, they also showed that the occupants were of the Moslem faith.
I understand Hand of Fatima door knockers are found extensively in Spain, which was under Moorish occupation for centuries. Some of the Moorish cultural influences penetrated as far as southern France, which is probably why you find them here, too. However, those you see today are probably 19th-century reproductions. I would be interested to know how widespread they are further north in France." ~ Life on La Lune