Construction system including perforated modular structural members

A construction system comprising:

• structural members of a first type comprising a first flange and a second flange merged at a right angle, each flange including a first end and a second end, the first flange including at least one row of spaced circular apertures extending longitudinally between the first end and the second end, a first oblong aperture at the first end and a second oblong aperture at the second end, and the second flange including at least one row of spaced circular apertures extending longitudinally between the first end and the second end;
• structural members of a second type comprising a single flange including a first end and a second end with at least one row of spaced circular apertures extending longitudinally between the first end and the second end, a first oblong aperture at the first end and a second oblong aperture at the second end;
• and
• structural members of a third type comprising a first flange and a second flange merged at a right angle, each flange including a first end and a second end with at least one of the ends closed by a web having an aperture, the first flange including at least one row of spaced circular apertures extending longitudinally between the first end and the second end, a first oblong aperture at the first end and a second oblong aperture at the second end, and the second flange including at least one row of spaced circular apertures extending longitudinally between the first end and the second end,
• wherein the structural members of the first type, the second type, and the third type are joinable together using fastening members passed through the circular and oblong apertures to form a structure.