"Archer's Knot": https://www.youtube.com/watch?v=vXu3NgWHMvA
A really handy knot where the loop stays fixed /w tension on the standing end, and the working end can be cinched to shrink the loop.
Fun fact: this knot seems to be the complement of the Arbor Knot (https://en.wikipedia.org/wiki/Arbor_knot), where standing end tension cinches the loop & the working end doesn't.
Also, handy rope terminology that really helped me out: https://www.ropebook.com/information/knots/terminology/
@kondziu I once had a girlfriend with a chain necklace knotted so badly that after days I still couldn't unravel it. So.. maybe!
@tty I guess I mean physically impossible. Like, it's too tight, or some trick of geometry makes something latch into place.
@kondziu Not sure if that qualifies for what you're thinking of, but: synthetic rope likes to melt more than burn, so sometimes I do a quick permanent loop by using a lighter to melt the ends together.
Sunbeam City is a anticapitalist, antifascist solarpunk instance that is run collectively.