My son wanted to create the animal rescue center from Go Diego Go so I offered to make a hammock for Diego to sleep in. This guide shows a 9-strand hammock, but I think using 12 strands would make it a better width.
Step 1: Cut and Tape the Strings
I used 9 strings about the length of my arm - the size depends on the size of your doll. Unless you have a very patient and helpful young person to hold the strings, I suggest knotting the ends and taping them to your table. My son was anxious for the results, but not so helpful in holding things still.
Step 2: Braid the End
I like the braids to go from one fat braid to two thinner braids to three thinnest braids. If you're doing 12 strands, you could even do four 3-string braids. This helps the hammock have a more oval shape, rather than going from the knot to the width of the hammock.
Step 3: Start the Knots
Starting from the left (or the right, if you prefer, I just find it easier to keep going in the same direction, left to right, left to right, rather than going back and forth) take the first two strings and knot them. Take the next two strings and knot them. Continue til there are either zero or one strings left. For the next row, leave one string untied on the left, then take the second string (from the first knot) and the third string (from the second knot) and knot them together.
Step 4: Anatomy of a Square Knot
Just in case you're not sure what kind of knot you should use, this is what I did. I started tying two strings together like I was starting to tie my shoe, but didn't pull it tight. Then, when I had it about where I wanted the knot to be, I did it again. I pulled the second one close to the first, adjusted the location of the knot, and pulled it tight. Sometimes I had to hold the tops and bottoms of the strings to get it tight enough. Sometimes it slid on the string and I had to slide it back. I also tended to let the knots get farther and farther away from each other when I got bored, so see if you can keep it fairly consistent. It doesn't have to be exact, since it is, after all, a toy.
Step 5: How Do I Know When to Stop?
Keep knotting until the hammock is long enough to hold the doll for which it is intended. And maybe a little bit longer, to give it a little give. It would be silly to do all this work and then not have it fit. (Why are you looking at me like that? It only happened once...) Then, start the braiding in reverse. Start with three (or four) braids of 3 strings each, then reduce the number of braids and increase the thickness until you have just one braid. Knot the end.
Step 6: Now What Do I Do With It?
Chances are your little one will have an idea where to put the hammock. My son wanted it in his animal rescue center tower, so I hung it through some holes in the side. It can also be taped, glued, or tied, depending where it needs to go.