A slippery hitch is a knot used to attach a line to a rod or bar. It does not provide great strength compared to some other knots, but it can be tied relatively quickly and released very easily. These characteristics mean that it is used on square-rigged ships for securing the gasket

Gasket (sailing)

In sailing, gaskets are lengths of rope or fabric used to hold a stowed sail in place. In modern use, the term is usually restricted to square-rigged ships, the equivalent items on yachts being referred to by the more prosaic "sail ties"....

s that bind stowed sails to the yards.

The slippery hitch is effectively a clove hitch

Clove hitch

A clove hitch is a type of knot. Along with the bowline and the sheet bend, it is often considered one of the most essential knots. A clove hitch is two successive half-hitches around an object. It is most effectively used as a crossing knot. It can be used as a binding knot, but is not...

 finished with a slipped loop. To tie one, begin as for a clove hitch, but instead of passing the end of the line through the loop in the final step, pass a bight

Bight (knot)

In knot tying, a bight is a curved section, slack part, or loop between the two ends of a rope, string, or yarn. The term is also used in a more specific way when describing Turk's head knots, indicating how many repetitions of braiding are made in the circuit of a given knot.-Slipped knot:In order...

instead, leaving the end on the original side. Pulling on this end will release the hitch. If tied in a gasket, this will quickly release the sail.