Step 4: Preparing the wall
The frame will be attached to the wall at 4 points: the two top corners and about half way down the middle on each side. Use the frame to mark these spots, drill holes and put the plugs in. At my balcony, the bottom of the frame is fitted against the tiles which lay on the balcony floor and wich stop about 10 cm from the wall. The tiles hold the bottom of the frame in its place. If this is not possible at your place, drill two more holes in the bottom corners, and make two more wood blocks to attach the bottom of the frame to the wall.
To protect the wall against the roots of the plants and against humid getting into the wall I put a piece of plastic sheet on the wall were I will later attach the vertical garden.