A structurally supportive device for constructing a weight-bearing feature in a wet area of a building, such as but not limited to a shelf, seat or step in a shower, bath, tub, sauna, spa or swimming pool, comprising a triangular horizontal support surface with first, second, and third edges, wherein the first and the second edges form a right angle; a vertical presentation surface depending down from the third edge; a horizontal support lip along a bottom edge of the vertical presentation surface; and attachment tabs protruding from the first and second edges, with each tab running at least two-thirds the length of the first or second edge; wherein the tabs protrude sufficiently far to be received into a slot formed into a wall surface finishing material but not so far as to penetrate a waterproof membrane or a wall board, and wherein the horizontal support surface and vertical presentation surface are configured to receive a feature finishing material such as tile, stone or solid surface material.