This knot is useful for when you do not have either end of your rope. It will not slip or bind. If both loops are loaded this knot can see a very significant load, because it reduces the stress each loop sees. It is also relatively easy to be able to be untied after removing the load.
Step 1: Start With a Bight in the Middle of the Rope
Step 2: Create an Overhand Loop
It will help you to bring the bight towards yourself if possible.
Step 3: Bring the Bight Under and Through the Center of the Loop
Step 4: Bring the Bight Around the Outer Loop
The outer loop is indicated by the X. Once this is done you will have something that looks like the second image.
Step 5: Bring the Knot Up Around the Entire Knot
When this is done you should have a loop around the two straight segments of the rope.
Step 6: Tighten Up!
This is the trickiest part of this knot. To begin fighting, pull the two pairs with X's on top until they are in place. Then tighten as needed.