First I rip the pieces to 5-5/8-in. wide. You can make them any width you want, but this is a great dimension because it makes a cover that will fit over a 4-by-4-in. treated post. You also get eight pieces from 4-by-8 sheet of overlaid plywood—enough for two 8-ft. long post covers.
Next I rabbet one edge of each panel with my dado blade, leaving a 16th or a little more of plywood intact. Bury the dado blade into a sacrificial rip fence so that you can cut a true rabbet to the edge. I remove 9/16-in. of the plywood leaving the rabbet to accept the adjoining piece of overlaid plywood.
Here is the dry fit after the dado work. Note that the thin tab extends the 1/16th or so beyond the adjoining piece. This will collect and catch all the epoxy and gather it into the crevice which is very important.
I stack the four panels on top of each other and stagger them to expose the glue joints. Then I hastily apply West Epoxy with the adhesive fibers mixed into the glue. I also apply epoxy to the edge that’s going to fit into the rabbet.
I lightly clamp the two ends to create the box. I use 2-in. masking tape to hold it together until the epoxy sets up. Pull the tape over the edge, creating enough tension to hold that thin piece of plywood to the butt end of the other piece.
I assemble the post covers on two sawhorses covered with transfer tape to protect them from the glue. If you don’t want to use clamps you can use stainless brads to just hold the four corners together until you’ve done all the taping.
After the epoxy sets up, I use a hand plane to trim the four edges. You can use a chisel or an orbital sander if you want.
Sand all surfaces with 80-grit sandpaper. Sand a slight chamfer in all four edges so that the paint will flow smoothly around the corners. Paint actually pulls back from sharp edges, leaving you a thinner paint film where you need it most.
Once sanded, it’s ready for primer and paint.
Here’s the end result—a very rigid, durable post cover that will fit over a 4-x-4-in. post.
