The 270-700 is a wall regulator installed inside a 4” x 4” electrical box. The box is fastened to a wall stud. The electrical box is covered with a stainless steel cover plate, from which a knob protrudes. This knob can be turned to control the inaccessible damper.
In effect, the 270-700 creates a “Manual Thermostat” Turn the knob one way and more air is delivered. Turn it the other way and Less air is delivered. What could be simpler?