Things You'll Need
Scissors or craft knife
A pyramid is a building or object made out of several triangles sitting on a base and angling in to meet at the top. Although the pyramid's sides are triangular, the base may have three or more sides. The more sides the bottom has, the more faces the pyramid will have. A pyramid with a triangular base is the simplest, most stable kind.
Cut a square out of cardboard.
Draw a straight line from each corner to the opposite corner on the square with your pen and a ruler, making an "X." The point where the lines cross is the center.
Cut from one corner to the center, using scissors or a craft knife.
Make folds along the remaining diagonal lines so the two triangles adjacent to the cut overlap. For example, if you made the cut between the pink and blue triangles in the diagram, fold the pyramid so the pink triangle is directly on top of the blue. You now have a pyramid shape.
Attach the two overlapping triangles by putting a layer of white glue between them. Hold them together until the glue dries.
Set the pyramid base-down on a cardboard scrap and trace around its perimeter. Cut out the resulting triangle with a craft knife or scissors. Apply glue to the bottom edges of your pyramid and attach the triangle piece to form the shape's base.
Use the metal edge of your ruler to press along the diagonal lines to make fold-lines in the cardboard that will bend neatly. Use a clamp or tape to hold your pyramid together while drying.
Monitor children while using a craft knife.