The standard types; how to use them. The best wrenches are forged from chrome-vanadium steel or high-carbon alloy steel and are heat treated, oil quenched, and nickel-chrome plated.
Pipe wrenches, monkey wrenches, and adjustable wrenches have movable jaws so that their spans change with the turn of a knob. Although versatile, they are imprecise: the movable jaw is a bit loose. In a pipe wrench, this feature is an advantage; when you apply pressure to the handle, the jaws tighten. In a monkey wrench, designed to grasp large plumbing nuts like those on drain traps, it matters little. But an adjustable wrench’s loose jaw can round off the corners of a tight nut or bolt head; use these wrenches for general work, but if you must apply much pressure, it is better to use a wrench that fits the nut or bolt exactly.
A box wrench fits over a nut to hold it firmly all around. An open-ended wrench grasps only three sides. Both are available in metric and fraction sizes; always use the exact size needed. A combination wrench has a box head on one end and a matching open end on the other.
A socket wrench set includes interchangeable socket heads in metric or fraction sizes and a handle with a built-in ratchet, so that you need not regrasp the nut with every turn of the wrench. The ratchet can be set to tighten or to loosen.