Blast gates are used to open and close branch ducts to divert airflow only to those machines in operation. This conserves air volume and keeps suction strongest where dust is being produced, thus maximizing dust extraction. Outer case made from cast aluminum with sliding steel gate and locking knob. Typical gate allow debris to accumulate in the groove preventing the gate from closing fully, causing leaking and reducing suction. The slot on these units extends through the back of the base to allow debris to be pushed out of the groove and prevent buildup.