I've never made mine out of a sock. I use canvas, cut in about a 5 or 6 inch square, sew ties on two sides, full length with the ends hanging off the top and bottom, left long until I've fit it. You can adjust the size of the square to what fits your bird best, smaller or larger. I put them on with the ties going parallel to the birds body, rather than accross, seems to work better for me that way. Tie one set in front of the wings and one set in back of the wings. I find that making them a bit larger makes them easier to fit and keep on properly. Mine look very similar to the one pictured in the second link I gave you before. I have cotton twill ribbon that I use for ties, and I sew it on for durability. It doesn't really matter what you use as long as it stays in place, supports the crop, and doesn't interfere with their normal activities. Some birds tolerate them very well, some don't. They may walk backwards, fall over on their back, etc while getting used to the idea, so monitor so she doesn't hurt herself. I had one bird that wore one for about 2 years. You do have to check regularly to make sure they are not rubbing or causing irritation, and under the bra can be a good place for mites/lice to hide, so checking for that too.