Bias tape is cut at a 45° angle to the selvage and is therefore stretchable along its length. It serves for easy finishing of fabric edges. Another feature is that bias tape does not require seam allowances. It is sewn around your fabric edges, so it does not alter the dimensions of your sewing project.

Bias tape is cut at a 45° angle to the selvage and can therefore be stretched lengthwise. It is used for easy trimming of fabric edges. Another special feature is that the bias tape does not require any seam allowances. It is sewn around your raw edges so it doesn't change the dimensions of your sewing project.