Position the horizontal “U” profile with the opening facing downwards, covering the ends of the vertical “U” profiles and the back support profile.
Using a drill with a ⌀ 5 metal bit, drill simultaneously:
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the horizontal “U” profile and the vertical “U” profiles in 4 fixing points: 2 in the front (left and right) and 2 in the back (left and right);
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the horizontal “U” profile and the back support profile in one fixing point.
Keep the profiles firmly in place throughout the drilling process to avoid their repositioning.

