How to Cut Keyholes in Foam Board
- 1). Open a compass to the width you desire for the round portion of the keyhole. Draw a circle on the cardboard with the compass.
- 2). Hold a ruler against one of the circle's sides, and draw a straight line down. Repeat on the circle's other side. Make the straight lines 1 to 2 inches longer than you wish the keyhole to be.
- 3). Angle the ruler near the bottom of the circle out, toward one of the straight lines you just drew. Draw an angled line, following the ruler, from the circle to the straight line. Move the ruler over, and draw another angled line from the circle's bottom to the second straight line. The distance between the angled lines depends on the size of your keyhole and your personal preference.
- 4). Hold the ruler so it intersects the two angled lines straight across. Draw a line along the ruler. Cut the keyhole out of the cardboard using the scissors.
- 5). Lay the cardboard keyhole template on the foam board. Trace around the template with a hobby knife to cut the foam board to that shape. Remove the keyhole shape from the foam board.
