Wrenches and spanners are hand tools that are used for turning, tightening and loosening nuts, bolts and other fittings. There is a variety of designs and choosing the best one for a particular task will make the job easier. The adjustable wrench is an all-round tool that is commonly used for general jobs. When possible, the wrench should be used in a pulling motion to prevent injury if the tool slips, and for the adjustable wrench, the force should be applied to the stronger, fixed jaw. A combination wrench kit with several sizes of open-ended and ring-jaw spanners is more suitable for larger jobs. Longer handles provide more torque, but shorter spanners can be used when working in a confined space. Socket wrench kits have a ratchet mechanism and often have an extensive array of attachments. The inserts can be connected directly to the wrench and an extension arm can be added to allow the insert to connect onto hard-to-reach nuts and bolts. With the use of adapter inserts, the socket wrench can also function as a screwdriver, and some kits even provide inserts for removing spark plugs. Torque wrenches are similar to socket wrenches but they include a display that shows how much force is being exerted on the fastener.