Acquiring a new set of specialized skills usually means learning a specialized vocabulary as well. That certainly holds true for the kitchen, where novice cooks and bakers must master a mixture of French phrases, archaic English words and a few ordinary terms with specialized meanings in the kitchen. For example, "scoring" has several meanings in ordinary conversation, but if a recipe tells you to score a ham hock or other piece of meat, it's a very specific instruction.
Keeping Things Superficial
In the culinary context, "scoring" a food means making a series of very shallow cuts on its surface. For example, a classic French pastry called the Pithivier is decorated with a series of shallow cuts that form a dramatic spiral when it's baked. Scoring is also widely used on meats, for aesthetic reasons or to improve their cooking characteristics in some way. The important characteristic of scoring is that the cuts must be very shallow, just penetrating the surface. Cutting too deeply usually spoils the effect, and can impair the outcome of your dish.
Getting Into Hock
The ham hock is a relatively small piece of smoked pork, corresponding to a human's shin. On the hog's leg it's located between the thin end of a ham and the ankle joint. This is one of the toughest cuts on a hog, filled with tightly packed, dense muscle and gristly connective tissues. However it's also very flavorful, and its skin and connective tissues add a great measure of richness and body to any dish. They're usually sold with the skin on, for just that reason.
Making a Score
If your dish makes use of the ham hock largely for the body it adds to a broth or sauce, you'll probably be instructed to score the hock's skin. This means making a pattern of shallow cuts just piercing the skin, which allows the skin's collagen to pass more readily into the cooking liquid. Some meals, especially traditional peasant dishes based on beans or sauerkraut, rely on the hock's fat to carry flavors throughout the other ingredients. In those cases you'll score the hock more deeply, piercing the skin so the fat can render and cook out, melding with the rest of the dish over the hours of slow cooking.
Although hocks are generally simmered to impart their flavors to other ingredients, they can also be slow-roasted in a gentle oven for several hours. Most such recipes will also have you score through the skin to the fat below, so it can render out during the roasting time. That helps the skin to crisp, becoming the lushly rich and sticky delicacy known to the English as "crackling." In a few cases you'll cut the skin away completely to reveal the layer of fat underneath. The fat itself is usually then scored into a crosshatch or diamond pattern, which speeds rendering. By the end of your cooking time the fat layer is reduced to a thin, crisp browned layer surrounding the tender flesh.