Sockets can be directly connected to the ratchet or first connected to a universal joint or driver extension.
Standard Sockets. Sockets are classified as regular or deep well. Deep well sockets can fit over the threads of a long bolt. Sockets, like wrenches, have points inside that fit over the fastener and come in both metric and standard sizes. Common sockets will have either 6-points or 12-points.
Specialty Sockets. Some sockets are specially designed. Do not use them on common nuts and bolts. For example, a spark plug socket has a rubber boot insert to hold and protect the plug from cracking.
Impact Sockets. Impact sockets are used where high torque and speed are needed, especially when using an electric or pneumatic (air powered) impact wrench. Warning: Never use a non-impact socket on a power tool. Always wear safety glasses. Impact sockets have thicker sides than standard sockets and are often black.