An employee was locking up columns that were approximately 10 feet tall so he could pour concrete. The employee was on a self-releasing line. His positioning belt did not latch properly and when he pulled on it, it gave way and he fell about 6 feet. His self-retracting line engaged, but he struck another employee who was working beneath him. On his way down, his tool belt hit a rebar piece, taking the cap off. The employee's armpit was impaled by the rebar.