When working with tools, especially with mechanics, it is important to always use the correct tool for the job. Channel locks have a variety of uses, but should only be used for certain tasks.
Channel lock pliers are a set of pliers that have an angled head where one handle slides to adjust the size of the opening used to pinch and grab without affecting the distance between the handles.
Channel locks, like any set of pliers, can be used to grip and crush items, such as crimping the end of pipes or other metal objects.
Channel locks can be used in a pinch to hold and turn nuts and bolts, but unless they are held just right, they will tend to strip the edges of the bolts.
Channel locks are excellent for grabbing and holding any irregularly shaped item and can often hold tight to rusted stripped nuts and bolts.
Channel locks are excellent for adjusting and tightening water pipes, especially when used in pairs--one set of channel locks to hold one pipe, with the other set turning the pipe fitting.