A source of confusion to many new buyers of Victorian homes is the difference between a register and a grille. Often the terms become interchangeable along with grates, air returns or covers. However there is a distinct difference of form and function between the two.
Registers are louvered to let air flow into a room (either hot or cold). Cold air registers are usually located on walls and ceilings while hot air registers are located on the floor as heat rises. A typical Victorian or early 20th century house in Ontario would consist of many registers but usually only one return per floor.