Wooden bins are preferable to plastic bins for outdoor worm composting. They don't degrade as quickly in the sun, and they are usually thick enough to deter chewing rodents. This bin is modeled loosely off of Mary Appelhof's 1-2-3 Portable Worm Bin, in her book "Worms Eat My Garbage." It will be 1 foot tall, 2 feet deep and 3 feet wide. The water catch tray will fill with nutritious drippings which can be used directly in the garden.
Measure all six of the 1/2-inch exterior plywood sheets, and cut them to the specified sizes with a circular saw. If you purchase the plywood from a home improvement store or lumber yard, they may cut it to specifications.
Mark a line 3 3/4 inches up the sides of the front and back panels, on the outside. Remember that the bin is 1 foot tall, so mark it on the 12-inch side.
Lay the plywood base on the four blocks. Lay the sheet of fine plastic mesh on the base. Cut the excess 1/2-by-1/2-inch corers off the plastic sheeting. Use wood glue under the overlaps on all the edges to hold the 1/2-inch overlap of the plastic mesh down over the sides.
Set the front panel perpendicular to the 35-inch side of your base. Your line should coincide with the center of the 1/2-inch thickness of your plywood base.
Use this line as a guide for inserting eight wood screws along the front panel, into the side of the plywood base. Repeat this for the back panel, then the two sides. You should only need six wood screws to attach each side panel.
Screw the edges of the side panels into the sides of the front panel and back panel. Three screws up each side should suffice.
Drill 12 holes, evenly spaced, with the 1/4-inch bit in the plywood base. All of the holes should be within the area of your tray. Drill three holes within the top inch of the two side panels and four holes along the top inch of the front panels. These air holes will keep your worms alive.
Glue one screening square over each of the 10 holes you drilled toward the top of the bin. Don't let the wood glue block the air holes. The screen keeps your worms from escaping.
Attach the bottom of the hinges to the top back of the back panel, so that you can attach the upper part of the hinges to the side of the lid. The hinges should each be a foot from one of the sides. Screw them in place securely.
Attach the hook screw from the hook and eye latch to the front center of the side of the lid panel. Let the hook dangle to see where it should sit when it rests in the eye screw. Mark this on the front panel, and screw in the eye screw here.
Leave the lid open to allow the glue to dry completely. Put the catch tray underneath it, centered, before adding bedding, kitchen scraps or worms.