Stretch cord

Stretch cord is an elastic cord, usually a clear or colored polyurethane or latex-core string, used to make bracelets that slip over the hand without needing a clasp. Beads are strung directly onto it and the two ends are tied together in a knot rather than crimped.

Sizing the cord to the bead holes matters: too thin and the cord can snap under repeated stretching, too thick and it will not pass through smaller beads. New cord also benefits from being stretched out by hand before stringing, since fresh elastic still has some give left in it that shows up later as a loose-fitting bracelet.

The knot matters as much as the cord itself. A simple square knot alone tends to slip loose over time, so most experienced beaders tie a surgeon's knot, an extra wrap through the loop, and add a small dot of glue before trimming the ends. A common mistake is relying on a single overhand knot, which can work its way open after just a few wears.