An interesting feature of a new industrial X-ray facility for Larpen Industries in Milwaukee is a sliding concrete door. The door consists of five tongue and groove site-cast panels, measures 10 feet by 9 feet and is 2 feet thick. Two sets of forms for the panels were used. The curing period was 7 days. Supporting the door was a problem. Four threaded rods were placed in each of the five panels and bolted to two heavy angle irons. By means of two large dollies the angle irons ride on an 18 inch I beam which is supported by four 6 inch H columns. The door is operated by a system of pullies and a 1 /4 horsepower motor.