Cleat Knot

The cleat knot, or cleat hitch is used to attach a rope to a cleat. A cleat knot is unlikely to loosen up but can be undone quickly if you need them to. This knot is most frequently used to secure a boat to a dock. It is also used for fastening halyards, dinghy bow lines, out hauls and down hauls.

Make a loop around the cleat making sure to go under the horn of the cleat furthest from the load first.
Once the loop around the cleat is done, cross over the top of the cleat and under the horn that you first went under.
(In the opposite direction) Complete the hitch by making an underhand loop and hooking it on the second horn and pulling the hitch taught.