A support device selectively disposed between a floor surface and a lower surface of distal end of a cantilever toilet in which a base defines a surface oriented at an oblique angle relative to a horizontal plane and with a guide rail attached to an upper portion of the base substantially parallel to the upper surface. A traveler operatively engaged to the guide member moves on the upper surface for selective positioning to bear against a lower surface of a cantilever toilet. A method of supporting a cantilever toilet is disclosed.