Between the dog days of summer, and moving out the fumes that accumulate when finishing a project, I needed to keep the air moving in my shop. So I made a simple air exchanger by stacking a couple of inexpensive box fans into the setup that you see above. The tower itself is a plywood frame attached to a base that’s mounted on a set of casters. The fans are held in place with brackets that are shown above. Since the tower is mobile, it allows me to focus the air-flow. A simple power strip attached to the side of the tower provides a place to plug the fans in. When shopping for the fans, I found a style that has the control knob on the face of the fan. This allowed me to size the frame to match the dimensions of the fan. You might have to adjust the frame and supports to fit the fans that you use. The base bracket anchors the frame to the base.