Parchment is most commonly made of calfskin, sheepskin, or goatskin. It has 10 times the tensile strength of cowhide and is 50% stronger than goatskin. A sheepskin or goatskin head is stretched and secured with glue, tacks or both. The djembe is headed with a rawhide skin, most commonly goatskin. Similarly, Heriot-Watt University uses goatskin parchment for their degrees. The zahato is made of two pieces of tanned and close-cropped goatskin. Dances are choreographed to the beat of goatskin drums and cowbells. They also wear grey blankets and goatskin skirts. A distinctive musical instrument is the damphu, a small round drum covered with goatskin. Traditional kefir was made in bags from goatskin. Boys usually ran around naked or wore a small front apron of goatskin. She is often shown armed and wearing a goatskin cloak. The goatskin used in today's A-2 is treated with a special fire retardant chemical. It is made of hardwood and generally has a goatskin hide. There, the drums are headed with goatskin instead of the cowskin used elsewhere.