Alpine Butterfly

It provides a secure loop in the middle of a piece of rope. 

Load can be safely applied in 3 different ways: 

1. from the loop to either end of the rope; 
2. between the two ends with the loop hanging free; 
3. or to the loop with the load spread between the two ends.

Pro features of this knot are that even after a heavy load it remains reasonably easy to undo and plus if you have a damaged rope it helps you isolate the damaged section so that the rope may still be used temporarily until you can get it changed.