A hollow polymer stall divider for use in a barn permits lateral flexing when a cow presses against the stall divider while the stall divider asserts a lateral force against the cow to urge the cow to move into a proper position between adjacent stall dividers without causing injury to the cow. The polymer stall divider can be formed of a single polymer material having a unitary density throughout. Alternatively, the polymer stall divider can be formed of multiple sections of different densities of polymer material, and different types of polymer material. The different sections of polymer material can be plastic welded together or connected by plug members inserted into the adjoining ends of the sections and secured with adhesives or other bonding material to form line blanks that can be heated until softened sufficiently to be bent into a proper shape within a pre-formed mold.
