Elastic is sometimes inserted in a fabric tunnel called a casing. You can create a casing by folding and stitching the fabric at a garment edge. Or you can apply a band of tricot (sheer ribbon) or bias tape close to the garment edge – at the waistline of a dress, for example.
To determine how much elastic you need, wrap the elastic strip around your bodyand add 1″ (2.5cm) for finishing the ends. Braided and non-roll elastic won’t twist inside the casing.

Edge Casing

1. Press the garment edge 1/2″ (1.3cm) to the wrong side. Fold the fabric again the desired amount to form the casing. Make the casing 1/4″ (6mm) wider than the elastic for easy insertion.
2. Edgestitch close to the top fold. Edgestitch close to the bottom fold, leaving a 2″ (5.1cm) opening near one side seam.
3. Secure a safety pin to one end of the elastic and insert it into the casing opening. Push and pull the safety pin through the casing until it reaches the opening. Make sure that the opposite end of the elastic doesn’t get pulled into the casing.
4. Feel along the casing to make sure the elastic is not twisted. Overlap the ends of the elastic and hand-stitch them together or machine stitch with a zig-zag stitch.
5. Stretch the elastic to pull ends into the casing. Edgestitch the opening closed, being careful not to catch the elastic in the stitches.

Applied casing

1. Pin the bias tape or strip of tricot that is 1/4″ (6mm) wider than the elastic over the marked casing line. Press under the ends 1/4″ (6mm) and abut the folds. Stitch close to both long edges.
2. Insert the elastic and stitch the ends together as for the edge casing. Ease the elastic back into the casing. Slipstitch the casing ends closed.