In frame-and-panel construction, solid-wood panels must be installed without glue to allow for seasonal movement. To allow that, and keep panels centered in the frames, commercial cabinet shops insert special neoprene rubber balls in the frame grooves. Here's an inexpensive method that works just as well.Buy a coil of 1/2"-diameter foam caulk-backer cord at a hardware store or home center. Slice 1/4"-thick discs, and place them into the frame-member grooves, as shown, four at the top and bottom of each panel and five at each side. Now glue only the frame mortises and tenons and clamp the assembly. The foam discs compress, centering the panel allowing for future movement.