Tayammum is dry ablution that can be performed if one cannot find water. It involves wiping the face and hands with clean dust or soil. The compulsory acts are making intention and wiping the face and hands, including the elbows. It is recommended to begin with Bismillah and wipe the face before the hands without long breaks in between. Tayammum can be done on earth-like substances but not materials like wood or metal. It is also permissible to do masah, or wiping, on thick leather socks.