It was a moderately low budget set design using cotton string from U-line, black paint, and lumber.
For the larger triangles, they suspended a caribeaner with black rope above the stage. Starting from one end of the base and working to the other end, they stapled the string to their base (approx 22ft x 1ft particle board painted black) and looped the string from the base to the caribeaner. Spacing each staple about 1-1 1/2 inch from each other. The short ones were made similarly. But instead of looping it to a rope hanging from the ceiling, they looped it around a 2×2 attached to the middle of the base (also 1 ft plywood that was various lengths).