The Bias is the diagonal line of woven fabric, where the straight grain and cross grain threads are at a 45 degree angle to each other. This is referred to as "True Bias" and provides the most stretch in woven fabric.
Benefits of Bias
Bias has much more elasticity or stretch than the straight grain or cross grain of woven fabric. In quilting, cutting fabric on the Bias is used when maximum stretch is needed, such as curved edge quilt bindings. Bias can also be a factor in cutting appliques when more flexibility may be needed to turn larger pieces under, such as in the outside edge of flowers and leaves, with the points on the straight of the grain, made from numerous fabrics.
Supplies and Tools for Bias
Bias fabric can easily be cut with a Rotary Cutter and Ruler using the 45 degree markings on the Ruler.
What I Wish I Knew When I Started using Bias
It is worth the extra time needed to cut the fabric on the BIAS and knowing about bias can greatly improve your patchwork. Bias Binding is needed for curved edges on quilts. It is also very helpful when cutting vines and stems for applique.