Some Important Things to Remember, an excerpt from Harriet Hargrave & Carrie Hargrave’s Quilter’s Academy Vol. 2 – Sophomore Year, p. 27:
When you start a new project, don’t forget to test your seam allowance. Using the fabrics of the new project, cut three strips of fabric 1-1/2″ x 6″. Sew two strips together and press. Check the width of each strip and trim if necessary. Attach the third strip and press. Measure the center strip; it should measure 1″ exactly. If it doesn’t, adjust your seam allowance as needed. (Volume 1, Class 130, Lesson Three, page 25).