Place the 24-by-30-inch wall cabinet on a worktable and remove the door. Measure from the bottom of the cabinet and make a mark on the sides of the front at 18 inches. Place the tri square on the marks and draw lines across the cabinet front.
Set the blade of a circular saw to 3/4-inch in depth and cut the lines. Tap the 18 inches of the front from the cabinet just cut with a hammer to remove it. Turn the cabinet on its side, measure up from the cut edge of the front that is still on the cabinet, and make a mark at 2 inches.
Drill two holes in the center of the 3/4-inch edge of the front with the 3/16-inch drill bit. Make one hole 3/4 inch from the bottom of the front and the next hole at 1 1/2 inches. Repeat this on the other side of the cabinet.
Put glue on the ends of the 2-by-20 1/2-by-3/4-inch lumber and secure it between the front sides through the pilot holes drilled with the drywall screws. Clean up the excess glue with a damp cloth.
Remove the shelf that is second from the bottom of the cabinet. Most cabinets have adjustable shelving, so this won't be a problem. If the cabinet has fixed shelving, cut down the center of the shelf from the front to the back with a jigsaw. You won't make it all the way to the back edge of the shelf, so tap on it lightly with a hammer to work it loose.
Secure the 22 1/2-by-15-by-3/4-inch plywood to the top of the bottom shelf with the wood screws. Install them from the bottom of the bottom shelf. Drill a 1 1/2-inch hole through one of the sides or bottom to gain access to the electrical outlet for the microwave.
Things You Will Need
- 24-by-30-inch wall cabinet
- Tri square
- Circular saw
- Wood glue
- 2-by-20 1/2-by-3/4-inch lumber (actual size), 1 piece
- Variable speed drill
- Philips head screw tip
- 2 1/2-inch drywall screws, 4 pieces
- Damp cloth
- Jigsaw (if needed)
- 22 1/2-by-15-by-3/4-inch plywood
- 1-inch wood screws, 4 pieces
- Cover the front edge of the new shelf with flat molding if desired.