Scrimshaw is the name given to scrollwork, engravings, and carvings done in bone or ivory. Typically it refers to the handiwork created by whalers made from the byproducts of harvesting marine mammals. It is most commonly made out of the bones and teeth of sperm whales and the tusks of walruses. The making of scrimshaw began on whaling ships between 1745 to 1759 on the Pacific Ocean, and survived until the ban on commercial whaling. The practice survives as a hobby and as a trade for commercial artisans. Scrimshaw essentially was a leisure activity for whalers. Because the work of whaling was very dangerous at the best of times, whalers were unable to work at night. This gave them a great deal more free time than other sailors. A lot of scrimshaw was never signed and a great many of the pieces are anonymous.