movable mount 12 as shown in fig4 and 5 having elongated slots 14 allows the hdpe panels 2 to expand and contract in a horizontal direction along the movable mount 12 the movable mount 12 directly replaces the non movable mount 6 shown in fig2 the hdpe panel 2 is bolted directly to the movable bracket 12 using bolts 8 and nuts 9 utilizing minimal torque on the mounting bolts preferably the bolts 8 and nuts 9 are corrosion resistant preferably the head of the bolt 8 is recessed in the hdpe panel 2 as shown in fig5 the bolts 8 and slot 14 are sized such that the diameter of the bolt 8 is smaller than the width of the slot 14 so that the bolt 8 can slide in the slot 14 a friction reducing and vibration dampening strip 16 is placed between the panel 2 and a surface of the movable mount 12 the hdpe panel 2 can expand and contract horizontally by the bolts 8 sliding in the slot 14 and the panel 2 sliding along the friction reducing and vibration dampening strip 16 the movable mount 12 is secured to the support posts 4 using clamps or other securing structure as desired the length of the slot 14 should be sufficient to account for the total horizontal expansion and contraction of all the hdpe panels 2 added together the width of the slot 14 can also be made sufficiently greater than the diameter of the bolt 8 to account for vertical expansion of one panel the vertical expansion will typically be less than the horizontal expansion since usually one panel is used in the vertical direction and multiple panels are used in the horizontal direction it.