Well you have caught me at a loss for words. I haven't ever heard that term. What I expect is you're referring to what we call a posterior splint. It's used for the 1st 24-72 hours until the swelling abates.
We get them ready made, accordian folded in several lengths, from a glute to toe, down to a colles wrist size and a full upper extremity.
I believe they are 6-10 layers of plaster fabric in depth.
We wrap with batting, cover with stockinette and then mold the posterior splint to maintain alignment. The whole is the wrapped with a 4" elastic bandage to hold the splint in place.
We use a pre-prepared plaster mixture that comes as a sheet (comes in various sizes). You open the bag, put lukewarm water in the bag, then squeeze the excess out and apply the splint and then hold it in place with Ace wraps.