The brake consists of a flat surface onto which the material is placed, and a clamping bar which will come down and hold the material firmly during the bend. This clamping action may be manual, automatic or operated using a foot pedal. The front, gate-like, plate of the machine is hinged and may be lifted, forcing the material extended over a straight edge to bend to follow the plate.

The bends can be to any angle up to a practical limit of about 120 degrees, somewhat more in the case of a bar folder. If the area to be bent is narrow enough, a sharper bend (e.g., for a hem) can be made by inserting the bend under the clamping bar and lowering it.

Box-and-pan brake[edit]

In a box-and-pan brake (also known as a finger brake^[1]), the clamping bar includes several removable blocks, which may be removed and rearranged to permit bending of restricted areas of a piece of sheet metal or of already partially formed pieces.

After bending, a box or pan form is then completed by screw, solder, weld, rivet, or other metal fixing process.

Bar folder[edit]

This is a simplified brake, usually much smaller than cornice or box-and-pan brakes. Typically, a single handle both clamps the workpiece and makes the bend, in a single motion, but the depth is usually much less than what a cornice or box-and-pan brake can handle.

Press brake[edit]

This is a more complex tool that forms predetermined bends by clamping the workpiece between a matching punch and die.