One of the things that makes English a difficult language to learn is that we have so many words that sound the same but mean different things. You will run into much of the same difficulty when you are learning to cook because the same foods can have different names and — even worse — different foods can have the same name. That's the case with pork, for example, where the difference between butt and shank often comes down to context.
The terms shank and butt are used for fresh pork as well as cured hams. If you are speaking of fresh pork, the butt is the upper part of the shoulder, and the shank is the lower portion. With a ham, it's the hind leg instead of the foreleg, but the terms are used in the same way.
Shank or Butt Ham
A full ham is made from the hind leg of a hog minus the narrow, gristly portion at the ankle. That section is called the "hock," and it's usually sold separately in either fresh or smoked form. The remainder of the leg is then cured in a wet or dry brine and smoked to turn it into ham. A whole ham is way too much pork for most households most of the time, so it's usually cut into smaller portions for retail purposes. Those portions are usually described as shank or butt ham.
The difference between butt and shank comes down to location. The butt portion comes from the top of the leg where it attaches to the hip. The shank portion comes from lower down the leg where the animal's thigh begins to taper. Both shank and butt have their good points and their fans. The butt yields larger, prettier slices, but it contains a bigger piece of bone and can be tricky to carve. The shank is chewier and won't give such large slices, but it's more intensely flavored.
There's More Than One Butt
That part is not difficult to understand, but, confusingly, more than one cut is referred to as the "butt." While both the butt and shank portions of a ham come from the animal's hind leg, the so-called Boston butt or pork butt roasts come from the shoulder, which is the animal's front leg. In this case, "butt" is a small barrel, which the roast was said to resemble. To complicate things even more, the shoulder itself is often smoked and cured to resemble ham. The end product is usually referred to as a smoked shoulder or a picnic ham.
The Difference Between Shank and Shoulder
A picnic ham is denser than the butt portion of a regular ham, which makes it more like the shank portion in texture and appearance. Like the shank, it's a bit tougher than the butt portion of a true ham, and it's harder to carve into pretty slices because it contains lots of small muscles running in different directions. That makes it hard to slice across the grain since the grain keeps changing. It's still plenty tasty, though, and often a lot cheaper than a proper ham.
Is Shank or Butt Better?
There isn't really a right or wrong when you're choosing between shank and butt portions of ham. It's purely a matter of personal preference, so on any given day your choice might be driven more by the brands available — some will always be better than others — and what's on sale. The best answer is probably to alternate between them a time or two, and see which appeals to you most. Once you've discovered which half you prefer, you can look for it whenever you're ham shopping in future.