Foundation vents are keep the air flowing and house cool during the summer months and closed to keep the underneath and pipes warm during the winter.
With the automatic vent, a person no longer has to remember to open and close the vent at the right times. In fact, the vent will even open and close based on an exact temperature, not just a time of year. A bi-metal coil opens and closes the vent when the temperature reaches a certain temperature. The vent will open at 70 degrees and close at 40 degrees without the need for a power source. There are also powered vents available that will accomplish the same thing but must be hooked to a power supply.
A few screws or anchors can hold automatic vents in place without any difficulty. They do not have to be cemented to the house, but a person should make sure that they are secure, so animals do not go under the house.