Truss

Trusses made for roofs are generally shaped like an isosceles triangle (something like this /_\ only imagine the two side lines to up to meet at a peak and the bottom line to meet the corners).

Commons
Trusses with this shape are called "commons". The two boards of equal length running up the side are called "top chords" and the bottom board is called the "bottom chord". The place at which the two top chords meet is the "peak". The place at which a top chord meets a bottom chord is called the "heel".

Plates
Of course, the boards involved must be attached somehow to one another. They are attached with are as "plates". A plate is basically a metal plate with sharp metal teeth attached to it. Plates come in various sizes as different coverage is needed for different joints on the truss. A given plate is refered to by its size; length by width. So, you'd say, "Yo, Tony, me a five by five for this peak!". Modern plates are coated with an oil to prevent rusting. The teeth on modern plates are arranged in a wave pattern to increase the "grip" a plate can get.

Webs
You'll rarely see a truss with only top chords and bottom chords. Most of the time, other boards are used to increase stability and better distribute weight and tension. These are called "webs". The most common web is the "king post" runs up the middle of the truss, from bottom chord to peak. Very few trusses are manufactured without a post. Other webs may extend from the bottom of the king post to the middle of the top chord on each side. These are called "side webs". Some webs stand upright like the king post but do reach the peak. These are called "uprights". The webs closest to the heel of the truss are called the "end webs".

Trusses made of steel are increasingly common in construction, though their presence is more widely felt in industrial framing than in residential. Steel trusses far stronger than wood trusses but require much more skilled labor in their production and installation as is much welding involved.

Truss (?), n. [OE. trusse, F. trousse, OF. also tourse; perhaps fr. L. tryrsus stalk, stem. Cf. Thyrsus, Torso, Trousers, Trousseau.]

1.

A bundle; a package; as, a truss of grass.

Fabyan.

Bearing a truss of trifles at his back. Spenser.

A truss of hay in England is 56 lbs. of old and 60 lbs. of new hay; a truss of straw is 36 lbs.

2.

A padded jacket or dress worn under armor, to protect the body from the effects of friction; also, a part of a woman's dress; a stomacher.

Nares.

Puts off his palmer's weed unto his truss, which bore The stains of ancient arms. Drayton.

3. Surg.

A bandage or apparatus used in cases of hernia, to keep up the reduced parts and hinder further protrusion, and for other purposes.

4. Bot.

A tuft of flowers formed at the top of the main stalk, or stem, of certain plants.

5. Naut.

The rope or iron used to keep the center of a yard to the mast.

6. Arch. & Engin.

An assemblage of members of wood or metal, supported at two points, and arranged to transmit pressure vertically to those points, with the least possible strain across the length of any member. Architectural trusses when left visible, as in open timber roofs, often contain members not needed for construction, or are built with greater massiveness than is requisite, or are composed in unscientific ways in accordance with the exigencies of style.

Truss rod, a rod which forms the tension member of a trussed beam, or a tie rod in a truss.

© Webster 1913.

Truss, v. t. [imp. & p. p. Trussed (?); p. pr. & vb. n. Trussing.] [F. trousser. See Truss, n.]

1.

To bind or pack close; to make into a truss.

Shak.

It [his hood] was trussed up in his wallet. Chaucer.

2.

To take fast hold of; to seize and hold firmly; to pounce upon.

Who trussing me as eagle doth his prey. Spenser.

3.

To strengthen or stiffen, as a beam or girder, by means of a brace or braces.

4.

To skewer; to make fast, as the wings of a fowl to the body in cooking it.

5.

To execute by hanging; to hang; -- usually with up.

Sir W. Scott.

To truss a person or one's self, to adjust and fasten the clothing of; especially, to draw tight and tie the laces of garments. [Obs.] "Enter Honeysuckle, in his nightcap, trussing himself." J. Webster (1607). -- To truss up, to strain; to make close or tight. -- Trussed beam, a beam which is stiffened by a system of braces constituting a truss of which the beam is a chord.

© Webster 1913.