Abstract: At approximately 1:12 p.m. on March 10, 1996, Employee #1, a carpenter's helper, was standing on the fourth step from the top of a new Werner, type I, 8 ft fiberglass ladder situated on a dry, level concrete floor. He was using a 16 oz fiberglass claw hammer to knock the top side of the left double-vertical 11 ft 5 in. high by 3 in. wide support beam toward the right vertical support beam. Both had 1 in. shims under them that were holding up a horizontal 7 in. high by 3 in. wide by 17 ft 9 1/4 in. long overhead main beam. Employee #1 was trying to take a true plumb vertical measurement from the bottom of the horizontal main beam to the floor. The bottom of the left vertical beam was already farther out from the wall than the to and the shim apparently flew out, causing the vertical support to gave way. The bottom of the ladder was knocked out from under Employee #1 and he tumbled 4 ft off the ladder, striking his head on the concrete floor. He suffered a baseline skull fracture, and was killed.