What is an adjustable wrench used for?

An adjustable wrench, also known as an adjustable spanner or crescent wrench can be used to release or loosen a nut or bolt. This type of wrench has serrated jaws, usually one fixed and one you can adjust to acquire the grip you need. There is no need to know the exact size of the bolt etc. as it is fully adjustable and extremely useful when trying to access difficult to reach places.  Thus making them a versatile addition to any toolbox.