Measure the wall or stage area for which you want to create a cardboard front. Decide how high your front should be. Let the purpose determine the height of the front; for example, if the finished front is going to be a western style bar, measure the cardboard so it is about 4 feet high. If the front is going to be a wall, make it double that or 8 feet high.
Cut the cardboard to the length and height you need with a utility knife. Tape cardboard pieces together with electrical tape along all the seams.
Paint the cardboard front to resemble the object or scene you need with acrylic paint. Let the paint dry overnight or for 12 hours.
Construct supports for the cardboard front while the paint dries. Cut a 2-by-4 wood board to match the length of the cardboard front. Line three additional 2-by-4 wood boards perpendicularly at the ends and middle of the longer 2-by-4. Connect the three perpendicular boards to the long horizontal one by hammering two size D wood nails through the horizontal beam into the ends of the three perpendicular beams.
Cut three additional 2-by-4 boards to reach diagonally from the ends of the three perpendicular boards to the back of the painted cardboard front. Hammer two size D wood nails through the diagonal boards at their bases, where they meet the perpendicular boards.
Cut three final 2-by-4 boards and place them vertically between the horizontal support and the diagonal support beams. Hammer two size D wood nails through the tops of the vertical supports into the diagonal beams. Have someone help you turn the support structure on its side so that you can hammer two size D wood nails through the bottom of the horizontal beam into the ends of the three vertical beams.
Apply wood glue or hot glue from a hot glue gun to the back of the cardboard front where it touches the wood support structure. Expect the structure to help hold cardboard fronts in place and keep them from falling over during your performances.