box brake (metal-forming shop tool). A metal-forming machine similar to a leaf, or cornice, brake. It is used to make straight bends across a piece of sheet metal.
The holding jaws of a box brake are made in the form of fingers. All four sides of a box can be formed on a box brake by allowing the sides that have been bent to fit between the fingers of the clamp while the last bends are being made. A box brake is also called a finger brake.
boxing of paint. A mixing procedure in which the pigment in a can of paint is thoroughly mixed with the vehicle. The paint is poured back and forth between two containers until the pigment and the vehicle are completely and uniformly mixed.
box wrench (mechanic’s hand tool). A wrench with an enclosed end shaped with six, eight, or twelve points to fit a square- or hexagonal-head bolt or nut.
Box wrenches can be used in close spaces, and they can be used to apply a greater force than can be applied with an open-end wrench.
Boyle’s law. One of the basic gas laws, which states that the product found by multiplying the pressure of a gas by its volume is always constant. If the volume of a container of gas is decreased without changing the absolute temperature of the gas, the pressure of the gas will increase.
brace. A part of a structure that supports or strengthens the main load-carrying portion of the structure.
brad. A thin wire nail with a small-diameter, barrel-shaped head.
brad-point drill. A special drill used for drilling cured Kevlar-reinforced composite materials. The tendency of Kevlar fibers to pull and stretch when they are cut with a drill is minimized by using a brad-point drill.

braid (electrical shielding and bonding component). A woven metal tube used to encase a wire carrying alternating current. This braid, called shielding, intercepts the electromagnetic field produced by the AC and prevents the field causing radio interference.