New weavers are often puzzled by the numbers that identify yarns: 10/2, for example, or 4,200 yd/lb. These numbers are very useful, especially when you want to weave a project that call for lots of yarns. You may not want to buy a whole cone to get just a small amount. Instead, you can substitute a yarn you already have, or a less expensive yarn, or a yarn you can purchase in small quantities. Here’s what you need to know.