Abstract: At approximately 9:30 a.m. on June 28, 1989, Employee #1 climbed up to the top of a single story 4-plex building unit to assist the other employees installing trusses. One truss was out of alignment and Employee #2 removed the nails holding the truss in place in an attempt to align it. The truss shifted and fell starting a chain reaction causing the rest of the trusses to topple. Employee #1 was struck and pinned by the trusses but was able to slide free and dropped onto the sub-flooring 8 ft 4 in. below. Employee #1 suffered a compressed disc and was hospitalized for three nights. Employee #2 was pinned between two rafters and suffered bruises and scratches to his arm requiring only first-aid treatment.