As Webster has told us, the gable is the end of a building. This is because the trusses that are usually used for the ends of roofs are called gable trusses. These trusses are kinda hard to build and have to be done pretty well.

The gable truss's structure is interesting. They consist of only top and bottom chords, uprights, and often a kingpost. All uprights must be placed at two foot centers along the length of the gable. This means that between the centers of each upright web, there will be two feet. Note that this does not mean that there are two feet of space between the uprights. That, if you do the math, is two-foot and four inch centers.

Building Gables
Firstly, of course, you lay out the outline of your truss. This means get the top and bottom chords where they need to be. Once this is done, you should jam your kingpost into position so you can be pretty confident that your height is correct. Now, all you gotta do is put in your uprights. Set 'em in, making sure they are at two foot centers from the kingpost. First, plate off the bottom because you can get that ninety degree cut square with the bottom chord. Now, drive the angled cut up against the top chord and plate it off. All uprights over four feet in length should get a 2x4 plate on the top and bottom. All others get a 1.5x4. Excellent job, my young tiger cub.

Why Gables Suck to Build:
The uprights are extremetly difficult to place at the required two foot center. It is not at all uncommon for your saw man to cut the uprights a little long or a little short, and as a result, the upright will not fit as it should. Mistakes like these are rarely caught in the production of gables. Let's look at the production: You drive the angled cut into the top chord. If the upright is an inch short, you are not going to notice unless you have spidey-sense. The only way you are going to catch this is if they are way too short or long, or if you do a bit of geometry and algebra to find out at what angle the upright and top chord should intersect given the pitch and height of the truss and the length of the upright.

Gables are pretty important things, so try to build them properly. The best workers in the plant should be assigned to gable duty. They are most likely to cut the wood properly, check for square and two foot centers, and keep the trusses uniform and pretty throughout the process.

Ga"ble (?), n.

A cable.

[Archaic]

Chapman.

Ga"ble, n. [OE. gable, gabil, F. gable, fr. LL. gabalum front of a building, prob. of German or Scand. origin; cf. OHG. gibil, G. giebel gable, Icel. gafl, Goth. gibla pinnacle; perh. akin to Gr. head, and E. cephalic, or to G. gabel fork, AS. geafl, E. gaffle, L. gabalus a kind of gallows.] Arch. (a)

The vertical triangular portion of the end of a building, from the level of the cornice or eaves to the ridge of the roof. Also, a similar end when not triangular in shape, as of a gambrel roof and the like.

Hence: (b)

The end wall of a building, as distinguished from the front or rear side.

(c)

A decorative member having the shape of a triangular gable, such as that above a Gothic arch in a doorway.

Bell gable. See under Bell. -- Gable roof, a double sloping roof which forms a gable at each end. -- Gable wall. Same as Gable (b).[ -- Gable window, a window in a gable.