EE was walking on grating that had been installed in slurry bridge. Crew was in the process of lifting the slurry tank agitator gearbox to do a test fit for the millwrights. Piece was overhead, EE was watching the piece and not watching where they were in relation to the open hole. EE stepped off the grating, there is a clip on the beam that EE struck shin on causing cut about 3"".