A socket extension is a device that allows a socket wrench to reach into hard-to-access places. Available in many different lengths, a socket extension fits between the ratchet and the socket to create a tool capable of reaching nuts and bolts in hard-to-reach locations. There are several different styles of socket extension designs, from wobble head extensions that allow the socket to turn off center on the extension to knurled extensions that provide grip when turning the tool by hand. Most extensions use a detent ball on the socket end to prevent the socket from falling off.
The use of a socket extension on a ratchet, the device used to turn the socket, and a socket wrench are not always to reach a fastener in a hard-to-reach location. Often, a socket extension is used simply to reposition the ratchet to a more comfortable position for turning. By using the extension, the ratchet is placed in a position a short or long distance away from the socket and away from other components that might make turning a ratchet difficult. An example of this might be using a socket extension when removing a water pump from a vehicle's engine in order to reposition the ratchet away from the cooling fan.
In many cases, the use of an extension between the ratchet and the socket diminishes the amount of torque that is applied to the fastener. The extension commonly twists under great load, thereby reducing applied torque from the ratchet to the socket. A common remedy for this reduction in power is to use a socket in a larger drive size to implement a thicker and stronger extension. The drive size refers to the size of the connection between the ratchet and the socket wrench, with a larger drive size utilizing larger components than a smaller drive size.
While the typical design of an extension is that of a solid steel makeup, there are also flexible socket extension designs that allow the socket to be turned on a great angle from the ratchet. This type of tool is capable of turning a fastener around a corner, however, it is not capable of breaking a stuck fastener loose. The fastener must be broken loose with a solid tool, such as a hand wrench, prior to the flexible socket extension coming into play. Consisting of a spring-like body, the flexible socket extension would simply twist and bind under severe torque situations.