Many years ago, when I was learning to cook more than just New England fare, I was using the original JOC. It was my husband's. There was a recipe in it for a Sunday Dinner Roast Beef. It called for to wrap the roast in caul. My husband told me that it was used to create and keep moisture in the meat. Then he explained to me in detail where it came from. He told me that you can use one from almost any farm animal. They would be the most readily available from a butcher. The pork one has the most fat.
It sounded like a lot of work to me, so I never gave it another thought until I would see other chef's on TV using it. But I still haven't used it.
Illegitimi non carborundum!
I don't want my last words to be, "I wish I had spent more time doing housework"