Barrel clasps are used mainly in the creation of necklaces. They can be purchased in real gold and sterling silver and are made in two parts that screw together. It takes a lot of practice to get the beading-thread knots in exactly the right spot. After you've done three or four, it becomes easier.
Unscrew the two parts of the barrel clasp.
Insert one end of the beading thread into one half of the barrel clasp. The threaded screw part should be to the outside. Tie at least two knots in the thread and push the knots so that they are securely inside the clasp.
Trim the loose end of the thread and apply one or two drops of jewellery glue on the knots. Use the tweezers to push the knots down if necessary.
String on all the beads that are required for the necklace you are making.
Insert the loose end of the string of beads into the unused half of the barrel clasp. Pull it as close as possible to the last bead on the necklace. Tie two knots in the thread. Cut the excess thread and apply two drops of jewellery glue to the knots. Use the tweezers when necessary to push the thread inside the barrel clasp. Screw the two barrel clasp pieces together to close the necklace.
Barrel clasps are available at craft shops such as Michaels and other stores that sell beads and accessories.