Channel:
Strut channel, often referred to colloquially by one of several manufacturer trade names, (e.g."G-STRUT", "Flexstrut", "Kindorf", "Unistrut", "SuperStrut", "UltraSTRUT", "Strut", "Metstrut", "JIKAstrut"), is a standardized formed structural system used in the construction and electrical industries for light structural support, often for supporting wiring, plumbing, or mechanical components such as air conditioning or ventilation systems.
Strut is usually formed from metal sheet, folded over into an open channel shape with inwards-curving lips to provide additional stiffness and as a location to mount interconnecting components. Strut usually has holes of some sort in the base, to facilitate interconnection or fastening strut to underlying building structures.
The main advantage of strut channel in construction is that there are many options available for rapidly and easily connecting lengths together and other items to the strut channel, using various specialized strut-specific fasteners and bolts. It can be assembled very rapidly with minimal tools and only moderately trained labor, which reduces costs significantly in many applications. A strut channel installation also can often be modified or added-to relatively easily if needed. The only alternative to strut channel for most applications is custom fabrication using steel bar stock and other commodity components, requiring welding or extensive drilling and bolting, which has none of the above advantages.

Shapes:
Basic strut channel comes in the open box section, 1 5/8 by 1 5/8 inch square cross section. A half height (1 5/8 inch wide, 13/16 inch tall) cross section version is also available, used mostly where mounted directly to a wall as it has significantly less stiffness and ability to carry loads across an open space or brace. A deep channel 2 7/16 inches tall and 1 5/8 inch wide is also manufactured.