Seven cards make a house with a pitched roof held beneath the wall tabs.
Why this level: Assemble six interlocking units, then match the roof width and the angle of its two retaining tabs.
You need: 7 matching business cards or cards (6 for the body, 1 for the roof)
A French newspaper in1931 showed how to make a card house. A card folded in half becomes the roof of a six-card cube, with its ends tucked under the upper tabs. Its first maker is unknown. Here we build the plain house without cutting the cards.
Did you know? One roof card leaves both triangular gable ends open. Two wall tabs bend to the roof slope and hold its ends.
Set aside one of seven matching cards for the roof. First build the body from the other six. Lay the red card sideways, white side up. Turn the blue card upright, coloured side up, and lay it across the middle of the red one. The white sides touch, and the overlap is a square.
Fold the right end of the red card up over the edge of the blue card and press it flat. Fold the left end the same way.
Turn the pair over as it is. Now the blue card is underneath.
Fold the top end of the blue card up over the edge of the red card and press it flat. Fold the bottom end the same way.
Open every folded end back to a right angle. Lift the red card off and set it down the other way up. Each card is now a unit: a square with a flap standing up on two opposite sides.
Make two more pairs the same way from the last four cards. Lay the yellow and blue cards sideways, white side up, and lay the red and yellow cards upright across them, coloured side up. Fold the ends of each bottom card up over the edges of the top card.
Turn both pairs over as they are. The red and yellow cards are now underneath: fold their top and bottom ends up over the edges of the cards lying on them.
As with the first pair, open every folded end to a right angle. Lift off the yellow and blue cards on top and set them down the other way up. All six units are ready.
Put one red unit in the middle with its flaps standing up. This is the floor of the cube.
Stand the two blue units up with their flaps pointing inward and lower them inside the red flaps. The red flaps hug the blue walls from outside.
Pick up the two yellow units and open the flap that will go at the bottom out flat. Stand the units up, lower them inside the blue flaps, then fold the opened flaps in under the floor.
Open the two top flaps of the yellow walls straight up. Turn the last red unit flaps down and lower it on top, its flaps going down outside the blue walls. Fold the yellow flaps back down over the lid. The cube is done!
Open just the two upper yellow wall tabs straight up. Leave the red lid in place.
Fold the seventh card in half and unfold, bringing its short edges together. This makes the roof ridge.
Bend along the centre ridge into a mountain. Adjust until the two ends are as far apart as the house is wide.
Lift the roof above the house. Lower both ends inside the raised yellow tabs until they meet the edges of the lid.
Fold the yellow tabs inward to match the roof slope. They cover the roof ends and hold the house together. The triangular gable ends remain open.