What does mean the front door in fez?

The front door (bab-i-dar)

"bab-i-dar"fez,Morocco

consists of a large door, rarely used, and a smaller door inside the larger one for everyday use. There are two iron door-knockers (kharsa)

(kharsa)

,
 one high up for those on horseback and a lower one for those on foot. There is a stylized hand of Fatima, to guard against the "evil eye", and an indirect entrance, so that strangers couldn't see inside the house. The bab-i-dar is decorated with simple linear or geometric carving and large round nails that attach the planks to the inner door frame. There is always one or two sets of inner doors at the entrance for security & privacy.