1.   A coal furnace provided heat up through metal floor registers.

2.   A furnace first heats air, then a fan pumps the hot air through metal ducts to floor registers in various rooms in the house.

3.   However, floor registers do little to distribute the heat properly.

4.   The specifications call for floor registers for hot-air heat.

5.   They are a shade more expensive than floor registers, but are worth it.