The rig was preparing to run 60” casing. The rotary was removed and a barrier was built by the rig welder and installed around the opening. The Driller and the Derrickman had discussed the need to rig up the rig’s choke line hose. The hose was laying on the main deck and needed to be hoisted up to the rig floor. At first it was decided to use the rig intercom system for communication. The Derrickman had proceeded to the rig floor to lower the rig air hoist and the Driller remained on the main deck to hook up to the choke line hose. The Driller decided to use hand held radios for communication instead of the rig intercom system. The Driller retrieved two hand held radios from the office while the Derrickman remained on the rig floor. When the Driller returned with the radios he threw one of the radios up from the main deck to the Derrickman who was looking through the opening left by the removal of the rotary table. The Derrickman caught the radio and fell forward toward the barricade leaning against the top railing. One of the barricade post collapsed causing the Derrickman to fall forward and through the opening landing on the main deck 25 feet below.