The Crash Preventer is a curtain of monofilament lines spaced 3" apart that mounts outside of windows or glass enclosures. The lines are factory-fastened to the rods and arrive wound around only one of the rods. The rods are square metal tubes that lock into square recesses in provided wall brackets. Two brackets support the upper rod and two hold the lower bracket. Four screws to install total. The installer places the rod with the lines on the upper two brackets and unrolls enough line to cover the glass area. No assembly is required.