Read the directions for making a paper airplane.

1. Gather a piece of paper approximately 8 x 11 inches in length.
2. Fold the paper in half, making sure that the corners are equal.
3. Fold the two corners at the top inward to look like two equal triangles.
4. Fold the corners inward again. Now each half of the paper should look like a dart.
5. Now fold the middle of the paper in half as you would a hot dog bun.
6. Lastly, fold the parts at the top downward. One side should be folded toward the left and the other toward the right.

suggests that the reader must have previous knowledge about shapes.
STEP 1?
STEP2?
STEP 3?
STEP 4?