Most of the times, when you cannot lock the handle/bar with the closing guide caps it is because the caps are reversed. The caps define the closing mechanism. The locking of the insect screen is characterized by the locking and interlocking of the cap placed at the very end of the handle/bar together with the closing cap guide.
Therefore most of the times when the locking mechanism fails is because:
Right cap is reversed with left cap of the handle/bar. The assembly instructions show the assembling of the plastic accessories on the handle/bar.
Vertical Roll-Up Insect Screen
Horizontal Roll-Up Insect Screen with High Bottom Truck
Reversal of closing right cap with closing left cap. Both for the vertical and for the horizontal roll-up insect screen, the failure to lock can be caused by the reversal of the closing guide caps. (base)
The curvature of the base is always visible to a person who, standing in the house, looks outside his home.
NB: the failure to lock the elements can be also caused by: a failure to“staple” the brushes, cutting mistakes, mistakes given by the out-of-square window opening.