1/ Cut a pentagon out of card. Drawn in the diagonals to make a smaller pentagon in the centre. 
2/ Draw the diagonals across the smaller pentagon, then extend them. 
3/ Cut out the five triangles at the edges. 
4/ Make a second copy of the same shape. Bend and open the card along the edges of the centre pentagon to loosen it up. Put the two shapes together as shown. 
Wrap a long elastic band around the edges, going in front of and then behind each corner. Release the shapes carefully... 
...TA-DAH!