Find a register that complements the decor and style of your home. There are many designs to choose from. Some register covers use air deflectors, which can divert air or shut a vent completely to regulate airflow. They can be purchased at most home improvement retailers.
Take your ruler or measuring tape and measure the opening of the air vent. Make sure to remove the old cover to get an accurate measurement.
Take the measurements and make sure your chosen register fits the duct opening. Most floor registers fit the standard size air vent opening.
Place your new register in the duct opening.