Bookshelves without holes and drills and screws

I needed some more space for books and I have found a few niches under the roof.

but I did not want to drill or screw into the wood from the roof truss when I remove the shelf at some point.

I have therefore opted for a solution with stainless steel cable ties. In addition, you need round wooden rods from the hardware store (I used 20 mm and 16 mm). The Open SCAD - File is included, so you can adapt it.

this is very stable, even though I only printed it with PLA.