Sidewall sprinkler head from another type. These small plates rest between the sprinkler’s orifice and the space it protects, shaping the water pattern as it sprays. While most (upright and pendent) sprinklers have a spoked circle, sidewall heads have a deflector that usually combines a semicircle and a flat plate that runs perpendicular to it. That shape guides water away from one direction and toward the intended direction.