The purpose of a wrench is to turn a bolt head or nut. Selecting the appropriate wrench depends on the fastener's design and size. It can also depend on how difficult the fastener is to reach. Wrench types include open end, combination, adjustable, and Allen.
Here's a tip: When using a wrench, pull it toward you rather than pushing it away. This gives you more control and reduces the chance of injury if the wrench slips.
Here are some of the different types of wrenches from which you can choose:
Box end. A box, or closed, end wrench is used where there is room to place the wrench mouth around the fastener. Box end wrenches are available in 6- and 12-point versions to match the number of sides on the fastener. Hexagon fasteners have 6 sides, or points, and are the most popular.
Open end. This type of wrench is used for turning fasteners in locations where a box end wrench cannot encompass the fastener.
Combination. A combination wrench has ends that perform specific tasks. One end may be open and the other closed, one may be offset and the other straight, or the two ends might be of fractionally different sizes.
Adjustable. An adjustable wrench can be used on a variety of fastener sizes. The disadvantage is that it is less stable than a fixed-size wrench and can easily injure you or damage the fastener. An adjustable wrench should be used only if the correct size wrench is not available.
Socket. Socket wrenches fit over the fastener, making removal easier and safer than with other wrenches. Sockets come in standard and extended depth; extensions are available to make removing fasteners easier. They are often purchased in sets by drive size.
Allen. Called by the Allen brand name, these are used on fasteners with a hexagonal hole in the head. Allen wrenches are available with L- or T-shape handles.