I added some measurements to the photo, if needed I thought i could get a piece of 3\/4" mdf and cut off the four corners and curve the inside using a jig saw and place one in each corner. Each one would fit between the two existing braces in the middle of each panel, i tried to show this with the blue lines i added. Thanks again\n\nYou won't need it. The 2 side panels fit inside the side with the rabbet. These help fit the joint together and are supported by the rabbet on the dadoed panel. The brace that you have already extends from the bottom all the way to the top at centre. So you have 3 contact points on each piece. I think you are good to go. If you're going to do it, I would just double check the 90 degree to make sure that it is accurate.\n\nnice diagram and thanks for the dimensions.