Double fold bias tape is a strip of fabric that has been cut on the bias and pressed to crease an off-center fold, as well as folded-under edges. There are two commonly accepted methods of applying double fold bias tape to encase a seam or the raw edges of an item. The first method results in obvious stitching lines on both sides of the tape. Using the second method, stitching on one side, is less noticeable.
Look at the bias tape to determine which half of the lengthwise fold is narrower. Keep the narrow side of the tape facing up while applying the tape.
Slip the bias tape over the edge of the fabric to be encased.
Stick pins through the bias tape and the fabric every few inches to hold the tape in place. When inserting the pins, also catch the bias tape on the underside of the fabric.
Sew along the inner edge of the tape as close to the edge as possible using a straight stitch on your sewing machine to stitch both sides of the tape in one pass.
Sew all the way to the edge of the fabric when you come to a corner. Then remove the item from your sewing machine and clip the threads. Turn the bias tape to create a mitered corner. Pin it in place. Reinsert the item in your sewing machine and begin sewing from the corner.
Unfold the bias tape so you can see the lines created when the bias tape was folded and pressed. You will have one center crease and creases along the narrow side of the tape and the wider side of the tape. When looking at the unfolded tape, the creases should point downward.
Align the crease that runs along the narrow side of the bias tape with the projected seam line of the area you want to sew--usually about 1/2 inch in from the raw fabric edge. Pin it in place. With the bias tape still unfolded, sew through the fabric and the bias tape on the bias tape's crease line.
Trim the raw edge of the fabric so it is even with the center fold of the bias tape. Fold the bias tape over the edge of the fabric. Pin it in place, catching the bias tape on the underside of the fabric.
Stitch in the seam created where the bias tape was sewn to the fabric. This method of sewing in the seam is often called “stitch in the ditch.”
If you come to a corner, sew all the way to the edge of the fabric and cut the bias tape even with the fabric edge. Leaving a 1/2-inch tab of bias tape extending over the top of the fabric, pin the unfolded bias tape to the next portion of fabric as in Step 2. Fold the 1/2-inch tab under to the other side of the fabric. Fold the bias tape over the edge of the fabric. Pin, trim and sew as described in previous steps.
If applying bias tape to a curved edge, press it to the finished shape with a steam iron before applying.
If you have trouble catching both sides of the bias tape after it has been folded over the fabric edge, use a narrow zigzag stitch rather than a straight stitch.