Wanted a hook that I could quickly attach to a tree or other post.  One end is captive, the other end goes through a cleat and just drapes over the hook to keep gravity from pulling it out of the cleat.  See the picture on how to route the rope.  

I used good quality paracord although it is important to note that some of the cheap paracord collapses into almost nothing and won't catch in the cleat.  The paracord should be long enough that it can wrap around wherever you want to use it twice but the good thing with this design is there's no need to cut to size.  You can even tie off one end through the hook and leave the other in a hank so you don't need to carry extra.

I put a good amount of weight on it without it slipping but it should not be used to hang or above anything that could be damaged or injured if it slips or fails.