The bias of a piece of fabric is a 45 angle from the selvage of the material. For this project the strips need to be 4cm wide and as long as the fabric will allow. You may need to join the bias strips to make enough to attach to the length of the neckline, do this by laying and stitching the two ends at right angles to each other, making sure that the right sides of the fabric are facing each other. When the bias is opened the strip will continue in one line. Pass the bias strip through a bias binding folder, pressing the folds in as you pull the folder along the strip. Carefully fold and press the binding in half again lengthways.