To solve the problems that a sewing cost is high for a tab curtain which is a style curtain, it is hard to open and close it since it does not slide well when a curtain body moves on a rail, ring runners which are accessory components are discarded without being used though they are devices for opening and closing a set of curtains for a decorative rail used for them, and a curtain without folds lacks in fanciness or the like.

The ring runner cover A is attachable to and detachable from a ring runner which is the accessory component of a pipe-like decorative rail.