Allows the use of Kallax glass shelves without needing to drill or screw into the shelf. It's also useful for sliding the glass in and out to remove things from the back.

I remixed this to fit taller 40k models such as Knights and Flyers on the upper shelf while allowing space underneath for smaller tanks and walkers. The shelf has a 12cm section below and a 22cm section above. 

If you want the shelf to be in the middle (16.5cm above and below) check out the original by Eric here: https://www.printables.com/model/467938-ikea-expeditkallax-glass-shelf-supports