This heavy-duty rail pointer set is built of durable aluminum stock and designed to last. The clamping blocks fit 1" EMT conduit (not included). The gauges are fastened to the conduit to establish the distance between the guide rails (DBG). As you move through the hoistway, set DBG at the same time as you set rail faces in correct relationship to each other. The longer pointer is mounted on a ball bearing with an easily adjustable alignment gauge.