IKEA Variera Stacker

I really love those IKEA Variera boxes. The problem is you can't stack them!
Adding some of the IKEA Variera stacker on each box, big or small, will solve this problem and the boxes can easily be stacked.
I use four times the 15mm version for the big boxes, two left and two right. Maybe one or two more in the back if the content is heavier or if your fear that the upper box will slide back and fall down.
For the small boxes three of the 10mm version was fine.