We used an anchor hitch in river rescue a lot but forget what its called.
At least three wraps around a tree and leave the working end loose or at least don't trap it under any tensioned part of the rope.
It is great because 1) it is very secure/won't slip 2) it is quick/easy to remove even after it has been under severe tension. I use it for hanging my hammoc or bivy shelter while hunting or any time I need a solid anchor. Its just a dumb simple solution -so it gets used.
What is a nail knot?
J-