How to tie it (The "Rabbit" Method applied to a running loop):
Pass the rope: Throw your working end around the tree or limb you want to choke.
Make the loop: On the standing part (the long line going to the ground), make a small loop (the "rabbit hole"). Make sure the standing part is on the bottom of the cross.
Run the rabbit: Take your working end (the tail) and pass it UP through that loop.
Around the tree: Go BEHIND the standing line (the "tree").
Back down: Bring the working end back DOWN into the hole.
Dress and Set: Hold the working end and the loop together, and pull the standing line to tighten.
Run it: Pull the standing line to slide the knot all the way up until it chokes the timber.