I learned to keep rhe pieces i cut from each pair of jeans together - in a zip lock bag or held together someway - because denim varies - a lot- from pair to pair of jeans.

Ha--today's jeans won't provide much fabric for cutting a good square! Remember when we would have been embarrassed to own, much less wear in public, jeans that are so raggedy? And those things are expensive to buy!! More air than fabric.