Tapered:
To become gradually narrower or thinner toward one end.

T-Astragal:
Astragal, T-like in shape, which is rabbeted to the approximate thickness of the swinging door.

Tempered Glass:
Plate glass with increased mechanical strength.

Threshold:
A strip fastened to the floor beneath a door, usually required to cover the joint where two types of floor materials meet.

Transom:
A small opening above a door separated by a horizontal member (transom bar) and which usually contains a sash or a louver panel hinged to the transom bar; the "transom bar" or "transom" may act as a door frame head jamb for the door opening and as a sill for the transom or may be built-up and separated; "transom" also refers to the "transom bar".

Trim:
Millwork primarily mouldings and/or trim to finish off (trim around) window and door openings, fireplaces, walls and other members.

Two-Step Distribution:
Traditionally, the customers of the millwork jobber have been the retail lumber and building materials dealer. This is know as "two-step" distribution.

U-Value:
The rate of heat loss is indicated in terms of the U-value of a window assembly. U-value ratings generally fall between 0.20 and 1.20. The insulating value is indicated by the R-value which is the inverse of the U-value. The lower the U-value, the greater a window's resistance to heat flow and the better its insulating value. See Heat Transmission Coefficient.

Veneer:
A thin sheet or layer of wood, usually rotary cut, sliced or sawn from a log, bolt or flitch.