Wrenches

A 12-point ring repositions every 30 degrees, which helps in tight spaces, but it bears near the corners and can round the head under high load. A 6-point ring grips the hex flats and transmits force better on rusted or high-torque fasteners.

It is the distance across the flats of the hex head, for example 17 mm for an M10 bolt to ISO 4032 or 16 mm to JIS. The same thread diameter can need a different wrench size depending on the standard, so check the actual fastener.

An adjustable wrench is handy for occasional repairs, but its jaw always has some play, so it is not suited to high torque. If you must use one, orient it so the load goes into the fixed jaw and close the movable jaw firmly before pulling.

A flare nut wrench has a slotted ring that passes over hydraulic, brake or air tubing and then grips the tube nut on five or six flats. This avoids rounding soft brass or steel tube nuts the way an open-end wrench can.

Wrench length is designed to limit hand force; a cheater pipe raises torque beyond the standard's test level and can crack the jaw or snap the shank. For high-torque bolts, use a properly sized socket drive or a striking wrench.

Cr-V (chrome vanadium) steel is hard and wear resistant and is usually bright chrome plated, which suits ordinary hand wrenches. Cr-Mo (chrome molybdenum) steel is tougher under shock, so it is common for striking wrenches and impact sockets. Steel grade is only one factor; heat treatment quality decides real durability.

The roughly 15 degree offset between jaw and shank lets you flip the wrench to get a new position when only about 30 degrees of swing is available. This makes turning hex nuts in narrow gaps possible without repeatedly removing the wrench.

The ratchet mechanism in the ring end lets you keep turning without lifting the wrench, which is much faster on long bolts or nuts on threaded rod. The mechanism carries less torque than a solid ring of the same size, so do not use it to break loose seized bolts.