This is a low quality product. I bought two bookcases. In assembling the first I found that some of the screws supplied were simply too short to secure the top of the bookcase (as shown in diagram 3 of the instructions). I also could not work out from the instructions how the back was supposed to be assembled. In the end I had to cobble together a solution. My experience with the second bookcase was much worse. The various components had been so poorly produced that they did not fit together properly. I ended up having to saw off part of the bottom shelf to make it fit to the upright. I also found that in trying to fit the various components together so much strain was put on the dowels that some of them broke. Again fitting the back boards was guesswork.