Step 1: Materials
2. Two lacrosse balls. They can be used or new. I suppose tennis balls could be used, but they are a bit bigger.
3. Cardboard. An old cereal box is perfect. We'll use this to make a mandrel to tie the knot around.
4. Duct Tape. You may also want some clear tape for taping the knot grid to the mandrel (see step #3).
5. Pins. In some of the pictures you'll see that I'm using threaded pins that I got from knottool.com: http://knottool.com/th_tubes.html. T-pins are actually a bit easier to use and more accessible!
Step 2: Print Out Knot Grid
It's dimensions should be 1952x2985. Now we need to print it at 300 dots per inch. If you know how to do that, then go for it and skip to the next step. I'll show you how to do it using the GIMP.
You can download the GIMP here (it's free): http://www.gimp.org/downloads/
Once you've installed it, open the image you saved and go to File - Print... In the Image Settings tab set the X and Y resolution to 300. It should print at about 6.5" x 10".
Step 3: Make the Mandrel
Step 4: Tie the Knot
From A1 . . . . . . . . . . . . . . . . . . . . . to E2
From E2 . . to D3
From D3 . . . . to F4
From F4 . . . . U . . . . . . . U . . . . . . . O to B2
From B2 . . to C2
From C2 . . . . to A4
From A4 . . . . U . . . . . . . U . . . . . . . O to E1
From E1 . O to D2
From D2 . O . . to F3
From F3 . O . . U . O . . . . . U . O . . . . . O to B1
From B1 . O to C1
From C1 U O . . to A3
From A3 . O . . U . O . . . . . U . O . . . . . O to E4
From E4 . O to D1
From D1 U O . . to F2
From F2 . O . O U . O . U . . . U . O . U . . . O to B4
From B4 . O to C4
From C4 U O U . to A2
From A2 . O . O U . O . U . . . U . O . U . . U O to E3
From E3 U O to D4
From D4 U O U . to F1
From F1 . O U O U . O . U . O . U . O . U . O U O to B3
From B3 U O to C3
From C3 U O U . to A1
Step 5: Double Up the Knot
Step 6: Cover the Lacrosse Balls
Step 7: Third Pass to Finish the Knot
Step 8: Other Rope Toys!
If there's one you'd like to learn how to make let me know in the comments and I'll put together an instructable for it! The last picture is of my puppy, Maggie, with a bunch of her used toys :)