To build a corner display shelf above the door casing in a room:
- Measure the room’s dimensions at that height. Mark a level line in both directions flush with the top of the existing door trim. Next, mark the locations of wall studs along this line on a piece of painter’s tape.
- Cut pieces of 1X2 to act as cleats between the door casing and the adjacent corners. The ends of the pieces that adjoin the casing are square cut while the fitting into the corner is a 45-degree angle cut.
- Attach the cleats so that they are both level and flush with the top of the door case molding.
- Attach a shorter piece of 1X2 to the side wall to support the outer edge of the shelf. This piece should have a 45 miter cut to match the longer piece in the corner. On the other end, “nip” off the lower corner of the square cut with a 45-degree cut where the end of the cleat will be exposed.
- The shelf board itself is a piece of 1X8. Make a 22.5-degree “rip” cut, angle up, along the front edge of the shelf using a table saw.
- On the top side of the shelf, create an 1/8-inch deep dado about 1-1/4 inches out from the wall. This is easily done on the table saw by making two shallow cuts side by side.
- Make square cuts on the ends of the shelf where they will terminate and 45-degree miter cuts where they will wrap around the corner. Match these mitered ends on a flat surface and draw two straight lines across the joint.
- Using a plate, or “biscuit” joiner, create a half moon shaped pocket in the edge of the shelf aligned with, and under each of these marks. The joiner should set up for the appropriate thickness of the shelf and the size of “biscuit” being used.
- Glue the edges and pockets, and insert the biscuit in one side of the joint before putting the boards into position and slowly tilting them down to engage the biscuit in the opposing side.
- Push the shelf boards in from either end to tighten up the joint. When the corner joint is tight the shelf can be secured to the cleat along its back edge.
- The front, angled edge is covered with a piece of small bed molding laid on its back. This creates a decorative lip along the front edge of the shelf to keep items from sliding off.
- Cover the joint where the shelf meets the cleat with a small piece of cove molding.
When everything is caulked and painted the shelf presents clean, attractive lines that provide a secure place to display decorative items, including plates.