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Among its basic uses are marking common, hip, valley and hip, or valley jack rafters, laying out stair stringers, determining and marking angles, and making square cuts on boards. Common lines made using a speed square include perpendicular cut marks and Angles definition of an angle for roofs, stairways, and decks. The tool uses a 0° reference.
Compass rafter: A rafter curved or bowed on the top (the top surface of a rafter is called its "back") or both the top and bottom surfaces. Curb rafter: The upper rafters in a curb (kerb, gambrel, Mansard roof) roof. Hip rafter (angle rafter): The rafter in the corners of a hip roof. The foot of a hip rafter lands on a dragon beam.
Hip, hipped: A hipped roof is sloped in two pairs of directions (e.g. N–S and E–W) compared to the one pair of direction (e.g. N–S or E–W) for a gable roof. Cross hipped: The result of joining two or more hip roof sections together, forming a T or L shape for the simplest forms, or any number of more complex shapes.
A knee wall is a short wall, typically under three feet (one metre) in height, used to support the rafters in timber roof construction. In his book A Visual Dictionary of Architecture , Francis D. K. Ching defines a knee wall as "a short wall supporting rafters at some intermediate position along their length."
Key:1: ridge beam, 2: purlins, 3: common rafters. This is an example of a "double roof" with principal rafters and common rafters. A timber roof truss is a structural framework of timbers designed to bridge the space above a room and to provide support for a roof.
The dragon beam lies parallel to and below a hip rafter and carries the rafter. The dragon beam is carried by the wall on the outer end and by a horizontal piece between the two walls on the inside end. There are conflicting usages for this term in the U.K. and U.S.A. (see below). The most common usage seems to be combination dragon beam/cross tie.
A simple timber frame made of straight vertical and horizontal pieces with a common rafter roof without purlins. The term box frame is not well defined and has been used for any kind of framing (with the usual exception of cruck framing). The distinction presented here is that the roof load is carried by the exterior walls.
A hammer-beam is a form of timber roof truss, allowing a hammerbeam roof to span greater than the length of any individual piece of timber.In place of a normal tie beam spanning the entire width of the roof, short beams – the hammer beams – are supported by curved braces from the wall, and hammer posts or arch-braces are built on top to support the rafters and typically a collar beam.