An employee was guiding a steel stair suspended from a crane hook into place to be connected with bolts. He used his sleever bar to guide and make sure the stair riser cleared the opening in the steel, but the top stair riser got hung up on the support beam. He pushed the stair riser with his foot. A clip angle on the stair got caught on the employee's pant leg and the stair swung back and caught the employee's right leg between the stair and the steel support beam. The leg was fractured above the ankle and required surgery.