Kayaks are single-passenger boats, traditionally used by Inuit hunters during the summer. The frame is usually made from wood, using driftwood and with Arctic Willow for the ribs. Originally, the frame parts would have been pegged and attached with sinew or sealskin cord, nowadays most people making kayaks use a nylon line. The frame is then covered with a waterproof layer of canvas or with the traditional method using seal or caribou skin. Most modern Inuit communities use boats with outboard engines, but occasionally kayaks are still used. There is an increasing interest in kayaking heritage and traditional skills are taught in workshops. An annual National Kayaking Championship is held in Greenland.