This particular post and video is for the two strand diamond knot which is doubled and includes an “accessory loop”. This acts as the bottom fixed knots on my side by side bead setups.
There are many applications of this knot; for example if you make a bight on a piece of parcord and use the two resulting ends to start this knot, then follow the same procedure you’ll have a simple neck lanyard with very secure loop to hold whistle, compass, knife etc. (like the last picture in this article http://khww.net/articles.php?article_id=57). This knot can also be doubled in a slightly different way to yield 4 working strands as in the top of my side by side beads – but that probably needs to be its own video.