Because a collar is sewn to a curved edge, it can be difficult to fit if the neck edge is not properly prepared. To prepare the neck edge for a collar, you will need to "staystitch". This means sewing about 1/8" inside the seam line of the neck edge as a first step. Then you will clip up to, but not through, the stitching at 3/4" intervals. This allows the neck edge to open up to almost a straight edge that you can easily fit the collar, hood, or other neckline addition.