Knot tying is a great skill to practice and makes a superb #10MinuteMake. This knot "the Alpine Butterfly" is of interest to me as I use it to tie loops in lines to attach parachutes too for rocketry. It's a good knot mechanically as it can be loaded on the loop and on either side. It can be tied into the middle of a line and also can be used to isolate a damaged piece of line or rope by tying the damaged section into the loop. Really handy! I found this copyleft license-free image that shows how to tie them.