The Reef Knot or Square Knot is quick and easy to tie; it is a good knot for securing non-critical items. Not to be trusted to join two ropes together. This knot was used for centuries by sailors for reefing sails, hence the name Reef Knot, and tying things aboard ship. It is important that this knot should not be used as a bend (for tying two ropes together). It is unsafe and can come apart. Be sure to form the square knot and avoid tying a granny knot, by making sure that both parts of the rope, the standing line and the free end, exit the knot together.