1 Jane Goodall: Something really weird is going on here. There's some sort of knot in the space-time continuum.
2 Steve: Crikey! What sort of knot? A reef knot? Bowline? Clove hitch?! Double crikey! It's a clove hitch, isn't it!
3 Rick: A clove hitch would only be a problem if time somehow had four corners.
4 Steve: Crikey! I read about that on the Internet! We're doomed!!

A clove hitch is, like all hitches, a knot used for tying a rope to a post. It's not a very secure knot for this purpose - there are much more reliable ones you can use. But it does have some application for particular purposes.

The one thing I remember about clove hitches from my younger days and reading about knots in a scouting book is that you should never tie your horse to a square post using a clove hitch. On a round post, the hitch will likely stay tied, but on a square post, it can very easily work itself loose if your horse moves around.

Not having a horse handy, I tried this for myself by tying clove hitches on to various chair and table legs. And it's true. If you tie a nice tight clove hitch around a round table leg, you can pull it any which way and it will pretty much stay tied. But if you tie one around a square table leg, you find that it very quickly loosens and unties itself if you pull the loaded end around the post.

I wanted to find a reference for this on the web, but Wikipedia doesn't mention this property at all, so a few seconds searching with Google turned this up.