A stab jacket usually has at least three plastic clips on it - two at the shoulder, and one at the waist.
A one-piece harness, by contrast, has no clips on it, and no plastic. It has only one release, which is a metal weight belt buckle on the waist strap.
A typical harness starts life as a piece of weight-belt webbing, around four meters long. It is important that the webbing be as stiff as possible - soft webbing twists up very easily, whereas stiff webbing stays where you want it.
The webbing is then threaded onto the backplate. In addition, another length of webbing, often a softer variety, is used to make a crotch strap.
In the above image, the blue webbing is the type I use on my harness. The black webbing is Halcyon webbing - not quite so rigid, but still stiff. The green webbing is the variety I use in my crotch strap - far too soft for use in the main harness.
This gives you a very simple and very strong harness to carry your wing and cylinders about. But very little else. To carry more kit, we need to be able to clip things on - we need D-rings. Once these are added, you have just one last thing to add: Bicycle tubing.
Backup torches need to be kept from swinging around. Easily done, by adding a bit of inner tubing, which you tuck the end of the torch into.
