Definitions of Terms under Alphabet B

Butt hinges are often referred to simply as butts.


A term usually used in masonry construction to describe a door frame or a sub-frame in a masonry opening, around which a steel door frame wraps and is fastened.


A molding- type of door casing. Used to trim the outside edge of an exterior door frame.


A small nail with a small head, usually used to fasten small trim and moldings, also known as a finish nail.


In door and sidelite assemblies, a term used to differentiate door and sidelite units which are first framed as separate units. Box-framed doors are joined to box-framed sidelites.

Boss, Screw Boss

A part that enables the fastening of a screw into the feature, thereby allowing assembly of the part with another. Screw bosses are common features of molded plastic lite frames and extruded aluminum doorsills.


A term used for the rubber part at the bottom or top end of an astragal, which beds the astragal end and seals between the end and the door frame or sill.

Ball Catch

A spring-loaded ball mechanism that is inserted into the top edge of doors that have dummy locks. The ball engages a plate on the header that has a dimple to receive the ball, which in turn keeps the door closed.

Ball-Bearing Hinge

A heavier-duty hinge than the standard hinge, with bearings supporting the pivots. Ball-bearing hinges are usually used for heavy doors that will be in commercial or industrial use.


Recess- or spacing, for locating a machined hole. The distance from an edge or surface to the center or edge of the recess.