Abstract: Employees #1 through #3 and coworkers were setting roof trusses. A mobile crane and a single nylon strap interwoven at the peak of the truss were being used to raise the trusses into position. Once the bracing between the previously installed truss and the newest one was in place, the nylon strap and crane strap were disconnected for placement on the next truss. Employees standing beneath the trusses then added additional nails to the bracing. As the nylon strap was being removed from a truss, it became entangled in the previously installed truss, lifting both trusses approximately 10 ft. The trusses returned to their original positions because of the pull of the bracing. The weight of the 1 1/2 in. wide bottom chord caused one of the trusses to break and strike Employee #1, who was working from a stepladder at the end of the trusses. Employees #2 and #3 were standing on the bottom chord and were struck by the truss when it hit a stair railing and bounced back at them. Employees #1 and #2 were hospitalized. The manufacturer recommends that a multiple-point line be used when installing trusses of this length (34 ft). The recommendation was also available at the office. The employees had not been trained in proper erection methods.