Here’s one way to secure an item using a rope that locks tension in the rope. It’s a variation of the Trucker’s Hitch. It involves creating a loop (slip knot) and then looping the free end of the rope twice through the loop. For the first, fixed end, I use a ring hitch knot which easily ties the first end of the rope to an anchor without it loosening.
Here’s how to tie a ring hitch for the first end.
Here’s how to tie the slip knot and trucker’s hitch with tension locking.
I found out how to do this from: