nudo ballestrinque/clove hitch

The clove hitch is a type of knot. It consists of two identical half hitches made successively around an object. It is most effective used as a crossing knot. Although it can be used as a binding knot, it is not particularly secure in that role.[1] A clove hitch made around the standing part of the line is known as either Two half-hitches or Buntline hitch, depending on whether half-hitches progress away or towards the hitched object.

Used as a traditional hitch, that is loading only one end, the clove hitch is liable to slip. It requires a load in each direction in order to be effective, such as when being used as a crossing knot. It should not be relied on with rope that is thin or very slippery, as it can work itself loose, especially under a swinging or rotating load. It can also jam and become difficult to untie under some situations.

To tie a clove hitch, first place a loop around the pole, with the working end of the rope on top. Run the working end round the pole once more until you meet the place where the ropes cross, then pass the working end under the cross. Pull to tighten.
A clove hitch formed in the bight and slipped onto a carabiner.

It can also be formed in the bight, that is in the middle of a rope, without either end available. To tie it this way, form two back-to-back overhand loops in a rope, and then put the top loop underneath the bottom one. Drop both loops over a post and tighten.