Abstract: At approximately 7:10 a.m. on May 31, 1991, Employees #1 through #3 and a coworker had just finished setting 13 roof trusses for a townhouse unit under construction. Each of the approximately 387 lb trusses was 38 ft wide by 10 ft high and was constructed of southern yellow pine 2 by 4s and 2 by 6s. As a truss was erected it was nailed on each end and held up by a single row of metal strap bracing that went down each side of the row of trusses. The bracing also maintained the 24 in. spacing between the trusses. The initial truss had been braced to an adjoining unit using 10 ft long 2 by 4s and an 8 ft long 2 by 4. Once all the trusses were in place, the employees were installing additional bracing when Employee #3 heard a popping sound overhead and noticed the trusses moving. Both he and another employee shouted a warning, but their coworkers were unable to get out of the way in time. Employee #1 sustained a fractured right leg, Employee #2 sustained a fractured collarbone and scalp laceration, and Employee #3 sustained a dislocated left hip along with left knee ligament damage. All three also sustained various contusions and abrasions. The main causal factor appears to have been inadequate bracing of the trusses.