A re-moistenable adhesive-coated drywall corner trim piece having an elongated semi-rigid core piece with a right and left flange, where the semi-rigid core piece has a centerline along which the flanges meet forming a hinge that can be bent and re-bent to any angle any number of times. The piece can also include a step running longitudinally along each of the flanges that can be located between the centerline and the flange edges so that the flanges change from a thicker portion toward the centerline to a thinner portion toward the edges making the piece boxable (capable of being wet mudded simultaneously on both sides without an intermediate drying step). Flanges can be curved slightly inward for perfect bonding.