Inuinnait have long used caribou sinew as thread for sewing. It is an ideal material as it swells when it needs to be removed. Sewing sinew is most often harvested from the tendons of a caribou's back. The coarser caribou leg sinew and marine mammal sinew are often braided into thicker ropes for fishing, hunting and domestic used.
Sinew is dried as wide sheets, from which long fibers can be peeled off as needed for sewing. Each strand is pulled through the mouth to remove its roughness and moisten it into a tightly rolled thread.