There are a variety of wrenches, but six of the most common are:  1. The standard wrench. This is the most common type and is used for a variety of tasks such as tightening screws, adjusting valves, and removing bolts. 2. The metric wrench. This is used for specific tasks such as tightening screws in metric measurements or adjusting valves in imperial measurements. 3. The Phillips head wrench.