Wrenches, important tools for basic maintenance and repair, come in various sizes and designs. Both standard and metric wrenches should be in a basic tool kit. Metric sizes commonly increase by 1 millimeter (mm), so a metric wrench set may have these sizes: 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, etc. Standard wrenches commonly increase by 1/16″, so a standard set may have these sizes: 1/4″, 5/16″, 3/8″, 7/16″, 1/2″, 9/16″, 5/8″, 11/16″, 3/4″, etc. Note: The double prime sign (″) is a symbol for inch units. The size corresponds to the distance between the two jaws in an open-end wrench.
Combination Wrench. A combination wrench has the two most common ends, a box-end and an open-end. Use the box-end whenever possible.
Wrench Ends. The box-end usually has 6-points or 12-points. Use the 6-point box-end when a great amount of torque is required to reduce the chance of rounding off the fastener (i.e., a nut or bolt). Note: Torque is a rotational force used to turn an object around a pivot point. An open-end is handy when the fastener position will not allow access with the box-end. If you need more leverage, use a longer wrench.
Adjustable Wrench. An adjustable wrench is a versatile second choice if a fixed-sized jaw wrench is not available. The jaw can be adjusted to fit metric or standard fasteners, but it does not fit as snugly as a fixed-sized jaw wrench. In addition, the head of an adjustable wrench may not fit in all locations and is not as strong. An adjustable wrench is sometimes called a Crescent® wrench (an industry brand name). If you are going to have only one wrench in your tool box, choose an adjustable wrench.