The yoke, or riser, on jeans is the v-shaped back seam section of denim jeans. According to Raw Denim, it gives the denim a curved seat. Different jean styles have different depths of yoke, allowing for different-shaped seat curves.
There are different types of yokes ranging from straight to v-shape. Designers use yokes to create different visual looks. The classic yoke is lower in the middle than the outer seams. This is the most traditional, and as of 2014, the most widely used variation. Cowboys traditionally wore jeans with a deep yoke. The deeper the v-shape of the yoke, the greater the jean seat-curve.