Cabinet Grade CNC track radius for a tambour door. Route your straight track and use these to make a precise 90 degree turn. The track is 1/2" deep and the block can be glued and mechanically fastened onto the inside case surface. Why do this when there are plastic parts that can be purchased? These are a better option because your product will be all wood. the track (straight and corner transitions will finish in  the same manner as the rest of the case.  Four corner transitions will allow your door to pass overhead and store vertically in the back of the case.  They come semi finished which is to say light sanding of the track is advised; the smoother the better. I recommend covering the bearing side of the track with Teflon tape to insure a frictionless door travel. The price is for a set of Two (2) Corner Blocks.