Solid wooden storage cabinet made of beech panels with aluminium profiles as column elements. Ikea products are Helmer and Lekman-Box.
Instead of the Lekman box, other boxes that match the measurements on Kallax shelf may be used such as Nornäs bookcase and sideboard Nornäs.
It is also possible to use wood panels from Ikea (table tops, kitchen countertops) but in my case it was cheaper to buy them at the hardware store.
For the aluminium columns I have chose a 40x40mm profile.
It already has a pilot hole in the center for a M8 thread and you can specify at purchase the required lengths.
With the help of threaded rods, the columns are connected together. The plates have holes of 9mm diameter for the threaded rods.
The nut on the right side is a special Rampa insert nut. This is needed to avoid visible screw heads on the top plate.