Abstract: The present invention includes several new embodiments of corner trim for use with vinyl or aluminum siding, which provide an appearance similar to that provided by the use of cast concrete corner stones at a fraction of the cost. The new corner trim is essentially a shell formed to have the appearance of a corner stone. Like the cast concrete stones it emulates, it is designed to fit over the corner of a structure. It may be manufactured from polymeric vinyl material via either injection molding or sheet forming process, or it may be formed by stamping sheet aluminum sheet. If aluminum is used, some welding may be required at the corners of the trim. A first embodiment of the corner trim incorporates a laminar, perimetric rim at the edges of the shell. When mounted on the building corner, the rim is perpendicular to the walls. A separate perimetric mounting strip is stapled to the wall sheathing on both sides of the building corner.