Called the "Texas Crutch" because some folks think it was developed in Texas, practically all the top competitive barbecue teams use this technique for ribs, pork shoulder (butt), and brisket.
First they smoke the meat for a few hours, then they wrap it in foil for a while. Sometimes they unwrap it and roast it again, sometimes they don't.
The concept is a descendant of the tropical technique of wrapping meat in banana leaves. It helps make meat more tender and juicy. It also has the added benefit of speeding the cooking process. It is a routine step in competition where every little incremental improvement is needed and if you are chasing that big prize money, you have to go for it. It is like a swimmer shaving his body.
On the downside, wrapping in foil can seriously damage the bark, the crispy exterior made of dehydrated meat, smoke, and rub, that is in many ways the best part of low and slow cookery. And you have to get the timing right. Too long in foil and you end up with mush.
If the meat is not in the crutch it takes longer to cook allowing more time for collagen to break down so in some cases the unwrapped meat can be as tender in the center as wrapped meat.
I never crutch pulled pork or ribs at home. The improvement is so small I just don't bother. It is more trouble than it is worth. But I always crutch brisket. I think it makes a significant difference. I know you saw it on TV. But until you master the basics, skip the Crutch.
Here's the science of the crutch
The idea is to seal the meat tightly in foil with just a little water, juice, wine, or beer. Apple juice is popular. The liquid mixes with the juices that drip from the meat and gently braises the meat. Braising is the same process used by a slow cooker where the meat sits partially submerged in a water based liquid. The liquid transmit heat to the meat better than air, speeding cooking.
Most importantly, the crutch prevents surface evaporation from the meat. Before and after wrapping, evaporation cools the meat, and that is what is responsible for the infamous "stall" a period of several hours where the meat's internal temp plateaus and beginners start to panic. With the crutch, the meat finishes cooking faster. Crutch for too long, and you will extract flavor from the meat, remove all the rub, and cause the proteins to get their undies in a bunch, forming tight knots that will make the meat tough and wring out moisture, and then eventually make the meat too soft and mushy.
Pull off a strip of wide heavy-duty aluminum foil about six feet long. Fold it in half until it is three feet long and make a canoe out of it big enough to hold the meat and so it will hold liquid without leaking. Pour 1/2 cup apple juice into the foil but not on the meat so you don't wash the rub off. Crimp it tightly over the top. It is important that the packet not leak liquid from the bottom, and that steam not be able to escape from the top. For ribs, place the slab on the foil meat side up being very careful that the bones don't poke holes in the foil. You can put the meat side down, but if you do, you may want to shorten the time in foil because the meat will be in the liquid.
You must seal the package tightly. No leaks. Use two sheets of double strength foil to be safe. In a fascinating series of experiments, the AmazingRibs.com science advisor Prof. Greg Blonder proved that if the crutch does not hug the meat, and especially if it leaks even a little, the meat will cool from evaporation and it will drastically slow cooking. He also points out that you should crimp the foil around your thermometer probe if it is inserted through the foil, and be careful to stick the meat from the top so juice doesn't leak out.
Brisket and pork shoulder. Crutch brisket and pork shoulder when the stall starts or when it hits about 150°F or 160°F and has a dark ruddy color, and leave it in foil until it hits 203°F. No peeking. The moment you open the foil it will start cooling rapidly. It could go from 203°F to 170°F in 20 minutes even though the cooker is 225°F. Don't let this bother you. The dirty work of melting fat and collagen has been done, so don't worry.
For ribs. I don't crutch ribs. The quality increase is small. In competition, you need all the help possible so you must crutch. If you are going to crutch ribs, be very careful that the bones don't puncture the foil. A double layer is recommended. People ask if they can put more than one slab in a package, but the effect will not be the same. You are essentially making a single thicker piece of meat and that will take longer to reach temp. Remember, thickness determines cooking time more than anything else. I don't recommend stacking.
On the rare occasion that I crutch ribs, I crutch for only 30 minutes. If you have heard of the 3-2-1 method, read the sidebar on the subject. I strongly disagree with the two hours in the crutch. Go much beyond 30 minutes and you risk overcooking the meat and turning it mushy.
You really can't tell when ribs are done with a thermometer. Click here to learn how to tell when ribs are ready. When the meat is ready you can paint on sauce, place it on a hot grill to caramelize the sugars, and serve. Click here to learn more about saucing strategies. If you wish, make Vermont Pig Candy with the liquid in the foil.
After the crutch. Some cooks put the meat in an insulated box, a faux cambro, to rest and further soften connective tissues. I think this is important for brisket. Less so for other meats. When you open the package be extremely careful to avoid the hot steamy air that will escape. Then remove the meat and cook at 225°F for about 30 minutes or so to dry the surface and firm up the bark. Finally, just before serving, add the sauce and put it back in the cooker or better still, roll it around on a hot grill if you are using a sweet sauce to caramelize it. Read my articles on pork shoulder (a.k.a. pork butt) for pulled pork, and brisket to learn more
When the bark is ready, you're ready.