On the feet, masah can be done over thick woolen or over leather socks known as khuffs, but according to the overwhelming majority of the jurists not on normal cotton socks. This is done when one has put on the socks shortly after previous ritual cleaning (called wudu), without having broken the conditions for that wudu, and time comes for the next prayer. It is then acceptable to wipe the covering of the feet in place of re-washing the feet. It is not permissible to do masah if the socks have significant holes. It is also done over one's headcovering in a similar manner involving the first three fingers. Additionally it is only permissible for a 24 hour period if at home, and 3 days if travelling.