A "barrel clasp" derives its name from the shape of the clasp. When the two ends of the clasp are secured together, the clasp looks like a barrel. On each end of the clasp there is a loop where the wire or line of the necklace can be threaded through. Barrel clasps are popular for bracelets and necklaces which need to be tightly secured because the clasp actually screws into place. There are also little grips on each end of the "barrel" which provide some traction as people try and loosen or tighten the clasp.
Lay the necklace out in the form of a circle so that each unfinished end is laying near each other.
Tie the end of your necklace through the bead tip. (This is sometimes referred to as a cup tip.) Using your needle nose pliers, string the end of the necklace through the bead tip and tie a square knot. Tie the string left to right, and then right to left. The purpose of the bead tip is to conceal the knot. Repeat this process on the other side of the necklace.
Place the bead tip through the circular opening on the end of the barrel clasp. Each barrel clasp will have a circle attached to it.
Crimp the bead tip down using your needle nose pliers. This will secure the bead tip around the circular end of the barrel clasp. Repeat steps three and four on the other side of the necklace.
Screw the male end of the barrel clasp into the female end until it is secure.
Remove any excess string or line by snipping it away with scissors. If there is any excess sticking out of the bead tip you can cut it off. For a tightly tied knot, there might not be any extra present.