Vintage Piping and Binding. I just could not resist 2 bags full of these cards.
Read more about bias at The Renaissance Tailor:
The Fear of Bias
Roberta Carr in her text Couture:The Art of Fine Sewing, speaks about 'bias':
"The fear of working on 'the bias' was ingrained in many of us at an early age. Some sewing teachers spoke of it as 'the enemy', never to be understood and to be kept at a distance. The bias is not a disease - it is a grain of cloth that when respected, can be used to advantage to produce remarkable results."