Curtain ring

Pliny's Natural History reports that the hard kernels of the cucus tree were turned to make the rings.

[1] Lewis and Clark took three gross of curtain rings with them on their famous expedition to the Pacific coast in 1804, expecting to give them as presents to the natives of the North American interior.

For example, they may be used as a wedding ring to solemnise a marriage ceremony;[4][5] or as a ligature to prevent nocturnal enuresis (bedwetting).

[6] Other uses include hanging a hammer from one's belt or attaching one's gloves or canteen to one's sleeping bag while camping when not using a backpack.

[7] The 1987 film Planes, Trains and Automobiles has a character played by John Candy who is a curtain ring salesman.