There are about four types of lines that are commonly used in interior design. One type of line is horizontal. These lines give a harmonious feel in rooms and a great transition between different rooms. Vertical lines are used to create a solid, formal, and lofty look. These make someone look up and admire the ceilings but too many vertical lines can make the room feel too enclosed and confined.

Diangular lines are usually associated with travel around the house especially in stairways. These lines, even though they are sharp and direct, look flexible and they cast important shadows that catch the eye. Curved lines are the opposite of diangular lines, they form a soft, graceful and elegant look. They provide a balance throughout the house even though you may only be able to see one specific line at a time it still feels balanced. Many architects use round or elliptical parts, such as archways to balance their designs.