This is something I designed quite a while ago and have never shared, as I felt it was something I made for only me and nobody else would use. I acquired a large amount 4ft x 8ft sheets of 6mm thick HDF material. I had no use for them and was trying to figure out what to do with them. That is why I created these connectors. I have built everything from a step stool to a raised water/feed shelf for my Mastiff to closet organizers and the junk shelf pictured. Use your imagination. The X, T, and L bracket are the main connectors you will use. The Top-Back labeled connectors are to add a top, back, or bottom (depending on your configuration) if you desire. The Mid Mount shelf can connect to any box and allow you to drop in another shelf. I printed everything with ABS so it would be a bit more flexible than PLA. I had to use a rubber mallet and tap them on too. I have been using these for probably 6 months and have not yet had one fail, and the stool pictured is quite large, at 16"x16"x16" and I am about 230lbs and have stood on it many times. I used a table saw and cut my material to size then used these connectors. Depending on your material thickness, you may need to scale these up or down. Simply print one to test, then scale as needed. Once you find your fit, you can scale them all that same amount. Enjoy, and feel free to reach out if you have any questions.