Step 3: Cut the Walls
Take two of the shiplap pieces, putting them together. We need a width of 11 1/4. Be sure to reserve the cut out portion for the back panel. The total depth of th cabinet will be 12". So, the side walls need to be 11 1/4" wide. Rip one piece for each side of the cabinet. Observe the knots on your boards, so they will not become a problem, either on a rip cut or where you will be screwing pieces together.
Screw each side wall together using the 1" x 2" pieces, which will become the cleats holding everything together. Use 4 - 1 1/4 screws on each cleat. the bottom cleat will be even with the bottom of the side and the other cleat 3/4" down from the top edge of the board. The cleats are 3/4" too short, this is to accommodate the wall cleats at the back of the cabinet.
Next cut the pilaster strip, the metal strips used to hold the shelves up, see the picture, into 24" sections and attach to side walls. I placed them up against the the top cleat so that they would be level with each other.
Next cut the bottom and top cabinet pieces. The wall cabinet is 1/4" shorter than the actual dimensions, so for a 33" wide cabinet, 33" - 1/4" offset - the thickness of the 2 walls 3/4" x 2 = 1 1/2". So the total length of the shelf will be 31 1/4", the offset will be made up for when we put the facing on the cabinet. Cut the top and bottom pieces and screw into the cleats using 8 x 1 1/2" screws. The extra long screws give extra strength to the cabinet. Be sure to pre drill for all screw locations.
Next cut and add ledger boards to the top and bottom of the back. The top Ledger board needs to offset to allow 1/4" space for the backing and the bottom one should go flush with the wall.
Most screws are in locations, where they will not be seen in the finished product.
Next cut the movable shelves, they should be approximately 29 3/4" long, check that they will fit in the cabinet easily. Cut cleats for the shelves and screw them together using 1 1/4 inch screws.