slotted angle

Generally made of 12- or 14-gauge galvanized, cold-rolled steel, slotted angle is available with a variety of perforations, and with equal or unequal legs. The shapes and placements of the holes are ingeniously chosen to permit pieces of slotted angle to be bolted together in countless ways.

Commonly available sizes are:

1¼ inches by 1¼ inches (sometimes called “125 angle”)
2¼ inches by 1½ inches
3 inches by 1½ inches

Commonly available lengths are

3 feet
4 feet
10 feet
12 feet

The holes in lighter angle accept ¼-inch bolts and heavier angle takes ⁵⁄₁₆-inch bolts.

Many large cities have firms that produce slotted angle to order.

Outside the United States, slotted angle is of course sized metrically. In the UK, the lengths tend to be soft conversions, e.g., 3048 mm (10 feet), but the thicknesses (1.75 mm, 2 mm, 2.5 mm) and dimensions of the legs (36 mm, 41 mm, etc.) are real metric sizes.