How to Make a Custom Seam Guide
What is a seam guide?
Your machine may have a built-in seam guide. Often the machine bed is marked with seam allowance lines in inches and/or millimeters. If you keep the edge of your fabric aligned with the marked guide, you'll be stitching straight.
Make a Stitching Guide
If your machine doesn't have a guide, you can add one. This easy-to-make guide can be moved or removed whenever needed. Stack several layers of masking tape one on top of the other to make a guide.
Position the Guide
Place a ruler under the machine needle. The needle should be directly above mark for desired seam allowance. (Sewing instructions indicate the seam allowance, such as 1/4" or 1/2" seam allowance.)
Gently lower the presser foot to hold the ruler in place. Align the guide at the edge of the ruler and press the tape stack in place.
Remove the ruler.
Place fabric under the needle with the edge abutting the guide. The guide acts as a ledge that keeps the fabric from wandering. Keep the fabric aligned with the edge of the guide as you sew, and your seam will be straight.