An air register is the cover on a duct. A duct system channels heated or cooled air, while the register controls the distribution of it into each room. Air ducts are hollow metal tubes. Air registers that fit onto one end of each duct are also usually made of metal, although some are plastic or wood. An air register usually has horizontal and/or vertical slatted openings; their direction and width determine how the heated or cooled air is distributed.
The slatted openings in air registers are called linear slots by manufacturers. Some air registers have one direction of slats or slots, while others are multi-directional. Some rectangular types of air register often have little levers located at the bottom of closable slats set in different directions. This format allows different sections of slats to be opened or closed to allow more or less air flow into a room. One-piece air registers with stationary rather than movable openings are usually sold as grilles or grills.
Grill or grille air registers are typically made of wood or metal. Many of these have wide, square holes rather than linear slats or slots in order to distribute a larger air flow. A wooden air register is the ideal choice for a duct located on a wood floor. Stainless steel or aluminum air registers may blend better on gray stone or slate floors. The different materials, colors and finishes of air grilles and registers allow home designers to create cool or warm looks to suit specific decors.
Many registers are rectangular in shape, but a type of air register called a diffuser is often circular. Diffusers spread out the air around the room, while slatted registers release it in streams. Diffusers are usually located on the ceiling or near the top of a wall, while rectangular air registers tend to be at the bottom of a wall near the floor. Many air registers are also located on floors.
An air register deflector is a rectangular, plastic low-sided device. It's designed to fit over a register located on a floor near drapes or seating. Without a deflector, the airflow from straight slatted air registers will rise upwards into the drapes or seating. The deflector blocks the airflow from moving upward and instead redirects it under chairs and curtains through the opening created by the deflector's low sides. Deflectors for air registers are very inexpensive and can be purchased for less than $15 US Dollars (USD).