Although we're going to connect only 9 dots, to illustrate what to do I've started with a square of 4 by 4 dots and numbered them 1 to 16 in rows: 1-4, 5-8, 9-12, 13-16. Join the dots in the following order: 8 12 (16) 11 6 (1) 2 3 4 7 10. The 9 dots you want to join are in 3 rows of 3 inside the 4X4 square: row 1: 2 3 4; row 2: 6 7 8; row 3: 10 11 12. The numbers in the brackets don't belong to the 3X3 square, because they're just to show which way you draw. You can see that the numbered dots in this smaller square all appear just once and you have used just 4 lines to join them without having to lift your pen off the paper!