Casings Base blocks and rosettes can be used. Our baseboard is cut on a 90° angle. Place the base block against the baseboard and glue or nail in place, depending on your preference. The casing should be centered on the base block and then nailed in place. Next, center the rosette on the casing, just like the base block, and then glue or nail in place. The top of the frame is cut at a 90° angle. It must be centered with the side of the rosette before being nailed in place.