I have no idea if this is a knot,
or knot system like the trucker hitch. it's easy to make quickly. after a heavy load it is super easy to untie.
Step 1: Make a Slip Knot
Just follow along here to make one Slipknot
Step 2: Make Another Slipknot Below That Slipknot
This is just showing you how to make the knot that I'm talking about
Step 3: Gather Slack From First Slipknot
Once you've pulled the Slipknot from the running and into the first Slipknot you'll end up with a loop that will hold under a load.
Step 4: How to Untie the Knot
Simply pull the loose or running the end of your line and the whole thing will come undone