Things You'll Need
Instructions
Place one strip of poster board on a flat surface. Fold it lengthwise two times. Unfold, leaving two creases. Bring the edges together and tape them. Once the poster board is taped together, the bottom should resemble a triangle shape, and it should be able to stand on end. Repeat this for the second strip.
Place both of the posts upright. Adjust them so they are separated by the length of a straw.
Using a pen, mark a spot four inches from the top of each post. Punch a hole in each post at the mark. Push the straw through the holes to make a crossbar between the posts. Reinforce it with tape.
Remove the straw from the holes when it's time to store the goalpost. For storage, place the posts, straw and extra tape into a small resealable bag.