A dog bone is a short, structural rod that can be attached to the end of a line. It's used like a button or toggle to make a connection to another line, grommet or deck fitting. The tapered middle and symmetric ends make the part look like a bone, hence the name "dogbone."
The dog bone is a very convenient way for attaching the halyard line to the headboard, as you can maximize sail height without the added length of a conventional shackle. It also works well for jib and spinnaker sheets, outhauls, the connection of soft loops used for attaching blocks to deck fittings, and numerous other rigging applications. Unlike a knot, the dogbone connection does not jam up under tension and can be quickly attached or detached.
