This design feature is unique to wooden clothespins. In high quality wooden clothespins, there is a larger hole furthest down from the stainless steel spring that is great for gripping most fabrics. Then there is a smaller hole closer to the spring that is used to grip thinner, more delicate fabrics without slipping.  Some wooden clothespins have two holes of equal size. Look for wooden clothespins with one hole smaller than the other (like these Heritage Clothespins) to ensure they have the ability to properly grip fabrics of all thicknesses.