Stackable Shelving system for filament sample

This is a Shelving system that will fit the alternative tray designed by Bas van der Ploeg to keep filament samples created by @Zahg and @Seemonster The filament samples were a perfect fit for my needs and the alternative tray was in the same lead, however, I needed to keep the trays together not warring about miss placing them or keep looking for them when needed so I came up with this simple shelve idea following these criteria Expandable adding more trays when needed (the Shelves are stackable, they will slide together make them one larger unit) Fast printing with minimal materials (originally, I designed this with hexagon opening in all five sides. I also tried it with full sold walls; however, with testing I found out that keeping the 2 sides with the hexagon’s and the other sides fully sold was the fastest approach with some material saved and it was the safest compromise between speed and weight) Keep the tray secured so they don’t fall out when the shelve is moved or pushed (I