I don't know how it is with girls, since I don't have any, but with 2 boys we are swimming in t-shirts. I took the stack that both boys have outgrown or that had holes from back in the day when Dharma had puppy teeth and would bite onto the back of their shirts. I cut each t-shirt in one continuous strip. Imagine peeling an apple and trying to get that long curly piece. I start at the bottom and then when finished, simply tie the pieces together to form one big ball of "yarn". The strips are about 1/2 inch in width and I just eyeball that part, it's not an exact science. Using a large crochet hook (I used a P) I single crocheted the rug to the size I wanted. I've started on another one for our entry way. I'm hooked, no pun intended.