sinew, which shrinks when wet, helps keep mukluks watertight. Commercial boots of modern materials will often require seam-sealing after purchase if they are to be fully waterproof. For insulation, mukluks may be lined with furs such as caribou, rabbit, fox and raccoon. Commercial sheepskin may be used to line and sole boots, as of the first decade of the 20th century. Down, polyester, and closed-celled EVA foam is also used in soft-soled boots. The inner boot may also be made of textile, or wool felt. Gallery See also Inuit clothing#Footwear Ugg boots Yup'ik clothing References Folk footwear Boots Inuit clothing Yupik culture