The dimensions of the steel frame of the plywood top are different from other BROR shelves (15mm length, 2mm thickness vs. 10mm length, 1mm thickness), and thus this clips will only fit on the plywood top.

Printing

I printed this out of PETG. The clips need to flex a bit when you install them. PETG works perfect in this regard - it will flex enough to attach the clip, but doesn't deform at all. 

Check output of slicer to prevent gaps inside (predetermined breaking point). Increase of “Sparse Infill Density”, setting the “Sparse Infill Pattern” to “Gyroid” and increasing the parameter “Infill/Wall Overlap” may help.

In addition, therefore I did set the option “Seam Position” to “Random”.

Some support may be needed.