I used up my last offcut of dyneema making another soft shackle. It is about 12" overall, which sounds a lot, but doesn't look too big when looped. No particular job for it, but I think it will come in handy.
Insert one end into the centre of the line, at the point where the lop will be. I have used a Swedish fid because that is what I have got. I can only do about an inch at a time, bringing the inserted end out of the side and then back in again.
I wrap masking tape round the end, to make it smooth and pointed. If I can't push it through the hole, I yank it through with the forceps.
Get to the final outlet eventually and work the whole thing to get it smooth and unbunched. The pen is through the loop just to stop it getting pulled closed.
I used a Biro to form a hole through one tail, which the other is passed through to lock the whole thing up.
The end is pulled through and the whole thing tightened and smoothed.
Then you tie a knot in the end, just like that. (Watch the video. It is actually quite easy. The main problem is making it more complicated than it needs to be.)
Putting a little leash in to open the loop really helps. I opened up the loop to the size needed to pass over the knot and formed a hole in the core length for the leash with my "fid".
The leash is just a piece of whipping twine passed through the hole and knotted. Pulling it back opens up the hole and the knot drops out. Very neat.
The finished job. I will put the loose ends in a vice and lean back to tighten the knot as much as possible before I cut the ends short. They recommend leaving about an inch on home made ones. The professional ones are tightened to several tonnes, and the ends can be cut off flush.