It's kinda like making sausage, but much easier.
It's used, as you've heard from these experts as a tool to make tying up roasts and alike the easier way but with less tying up time.
You simply open up a meat netting's 'sock', wrap it over the thin end, insert your rolled protein at the other end and shove it through until it's encased by the mesh. The 'sleeve' expands to incorporate the protein.
Initially, be sure to tie a knot at the end of the desired length of mesh, and after the protien is encased, spin the other end, tighten it up, tie it up snip, and you're good to go.
BeIt