Ok this might be a stupid question but how the heck doe Sewing Machines Parts and Sales in Los Angeles

Like others said, it’s knit in the round, and then cut for the arm and neck holes.

A lot of knit bought at the fabric store is also knit in the round. Usually it’s cut down one side so it can lay flat, but I’ve also bought still round lengths of fabric.

Your shirts however are made in certain sizes so that all sizes of shirts don’t need seams. It saves time, because the factory works cut less, and don’t sew side seams, but it only works for men’s shirts, which don’t have the waist shaping that womens shirts do.