Best way to shorten a dress without sewing Prom Dress Alterations: Get Ready to Shine on Prom Night! Your prom dress should fit you perfectly and feel as special as the night itself. Professional alterations can make sure your HOW TO LEVEL A HEM without a mannequin. , 1. Sew your skirt to into the bodice of the garment. , 2. Hang up the garment, and let it settle overnight so that the fabric can drop., 3. Measure out Open Back Long Prom Dress with Mermaid Skirt Forest Green Medium