According to a U.S. Department of Labor publication the problem of protruding steel rebar is one of the top physical hazards OSHA inspectors found on construction sites. In conversations with construction personnel, OSHA investigators reported hearing many accounts of situations where an employee had fallen onto a piece of steel rebar. Outcomes ranged from serious internal injuries to death. OSHA approves a number of devices for covering the ends of exposed rebar. The most common protective covering is a plastic cap, which has a rounded surface that faces upward. When rebar are arranged in a row, some contractors set a piece of lumber on top of rebar ends to provide protection. But unless the lumber is secured to the rebar in some way, there's a chance it will be knocked off.