In the case of a horizontal roll-up insect screen in the assembly instructions, it is always written to place de compensation spring (M) upwards. The compensation spring (M) should tend to push the dumpster down in order to properly work.
NB. It is important that, in the horizontal roll-up insect screen with raised guide, the Allen screw is tightened only in the upper cap (do not tighten the lower cap screw).