Bulkhead frame couplers, also known as terminal bolts or anchor bolts, are made to attach to a panel or frame so that air can pass through that barrier. They are usually used on air brake lines on heavy trucks and equipment. They feature a steel zinc plated body and nut for corrosion resistance and a steel internal tooth lockwasher to anchor it in place when tightened. They come in alternating male/female pipe sizes for different applications.