The hem on many wedding gowns is created with a horse hair braid. The braid is not actually made from horse hair, but is a synthetic nylon or plastic braiding. Horse hair braiding can be purchased in a variety of widths and is typically between one and two inches wide. The horse hair braid is flexible but creates a slightly stiff hemline, adding shape and movement to the skirt. Many wedding gowns use a horse hair braid hem to keep the long train of the gown in the proper shape and allows you to move more easily in the dress.
Mark where you need the hemline to be. You can either pin up the fabric to mark the new hemline or you can use a washable fabric marker to mark the hemline. Some fabrics stain from fabric markers, and you cannot get rid of the mark completely. Ask the dress shop or fabric store about your fabric or purchase a test square of fabric before marking directly on your dress.
Trim the excess fabric approximately 1/4 inch below the new hemline you marked. Measure twice and cut once. If you cut the hemline too short the dress will not fit you properly and you will need to add lace or other fabric to fix your mistake, which will be costly in terms of money and your time.
Align the top of the horse hair braid with the new hemline you have marked. Start placing the braid on the back side of your gown along the seam. Fold the starting end of the braid underneath of itself along the dress's seam. Run the braid along the entire hemline.
Stitch the braid along the marked hemline. You can do this by hand or by sewing machine depending on your skill and comfort. You can use a simple running stitch to stitch the braid to the hemline. Make sure to keep the edge of the braid aligned with the marked hemline edge. Fold the finishing end of the braid underneath itself, similar to how you folded the starting end. The two folds should now by lying next to one another.
Fold the hemline up so that the wrong side is now along the hemline marking. Edgestitch along the folded side. Depending on the fabric and bulk of your dress this may be more difficult to do by hand because you have to stitch through all of the layers.
Tack the horse hair braid's free edge to the seams. To tack the braid use a tacking stitch in a cross pattern. Once the braid is tacked you can whip stitch the two folded ends along the seam. A whip stitch is accomplished by passing the thread over the edge of the fabric diagonally, without going through all of the fabric.
Press or steam the new hemline completely. Be careful that your work surface is clean and large enough to move the gown. If you are using a flat iron be aware not to scorch the fabric. Touchless steamers can achieve a strong hem without damaging the fabric.