Side tension rails to control bale length variation in a square bale chamber

An improved mechanism for controlling the pressure applied by the side walls of a square bale chamber comprising two independently positionable opposing pairs of bale tension rails, each pair perpendicularly arranged with respect to each other, whereby a uniform pressure may be exerted on all four sides of the bale in the bale chamber thereby resulting in improved consistency in bale length, density, shape, and appearance.