A fair number of older adjustable razors just use the blade as the tensioner. The older blades were thicker and as a result had more spring in them so they worked fine. Current blades are a lot thinner and have less spring in them, so the same idea no longer works. If you loosen the head too much it just rotates freely. This was an idea that I came up with to lock the top cap in place which, coupled with the locator pins stops the bottom plate from rotating.

That said, when the Bates arrived some time later, I saw that it uses the same system. As it's only used on one head, they added numbers, markings and a stop. There's nothing really new in the World of shaving - is there!

Its very simple to use, loosen the main part of the handle until you have the gap that you want and then tighten the twist knob and lock the head in place. Once I got used to it, I find that it's pretty easy to adjust on the fly.

I use it on a number of heads.
I've found that the more curved or torqued the blade is the better it works.

Hoffritz Superslant This has a unique thread so it has its own dedicated locking handle.
Phoenix DOC Ascension It has its own page HERE however I prefer using it with the locking handle.
Seygus Zeppelin The Seygus is probably one of the nicer heads to use as it torques the blade in two directions.
Stahly Live Blade This head has a "floating type" of arrangement which helps keep tension on the blade itself. Its a very smooth shaver.