There are two basic types of machines that can be used to make homemade pasta — the roller type and the extruder type. Roller-type pasta machines come in hand-cranked and electric versions. Both come with several attachments — usually one pair of smooth rollers for rolling out the sheets of dough, and two notched pairs (one narrow and one wide) used to cut noodles. With this type of machine, the dough is run between the smooth rollers at increasingly thinner settings until it reaches the desired thickness. The sheets of dough are then fed through either pair of the notched rollers, which cut them into noodles. Some machines have additional attachments, such as crinkle-edge cutters for making lasagne noodles. Extruder pasta machines mix the dough inside the unit, then force it out through special plates with variously shaped perforations. Depending on the perforations, solid or hollow-shaped pastas can be produced. Both types of pasta machines are generally available in gourmet kitchenware stores and the small-appliance section of many department stores.