Before electric washing machines, and even before hand-crank washing machines, laundry was scrubbed on a rough surface between two pieces of wood. The apparatus was known as a washboard. During tough economic times, the washboard is still a dependable method of removing clothing stains. The following steps will lead you to being a proud owner of your very own DIY washboard.
Prepare Side Boards
Draw a line down the exact center of each 2-by-4 board, from one end to the other.
Measure 3 3/4 inches from each end and draw a line straight across from edge to edge, forming a cross-hair "x marks the spot" where the lines cross.
From the center of one of the crosshairs on either end of the 2-by-4, measure 5 1/2 inches further down the center line and draw another crosshair line. Repeat this step once more. You should end up with four crosshairs spaced equally apart between the two ends.
Perform all of the above steps to the second 2-by-4.
Use a hole saw that will cut a hole at each cross-hair. Each hole should be slightly smaller than the outside diameter of the dowels you chose to use for your washboard. The dowel ends can always be sanded down slightly for a perfectly tight fit, but the holes cannot be reduced in size once cut. Place the hole saw bit in the center of each crosshair and drill each hole completely through each location on both 2-by-4 sideboards.
Forming the "Ladder"
Slide the ends of the dowels into each of the four holes on one of the 2-by-4 side boards. If they won't go all the way through, lightly sand down the last inch and a half of the dowels until they go all the way through each hole. The end result you are looking for in this section is to create what appears to be a miniature ladder with the dowels serving as the rungs of that ladder. The dowels shouldn't protrude visibly from the outsides of the side boards. Repeat this step for the second 2-by-4 side board and the other ends of the dowels.
Disassemble your "ladder" by removing all of the dowel ends from both boards. Apply a generous amount of wood glue to the insides of the holes and also to 1 1/2 inches on the ends of the dowels. Reassemble the glued dowel ends into the holes and make sure the dowel ends are evenly flush with the outsides of the side boards and let the "ladder" joints to cure for 24 hours.
Within just three hours after beginning the joint curing segment, apply three to four coats of flax oil to all exposed areas of wood. Cover the entire ladder generously to seal and waterproof the wood. Allow the flax oil to dry for the remainder of the 24-hour curing period.
Install the Wash Surface
Place the piece of plywood between both of the 2-by-4 side boards and press down onto the dowel rungs. The ends of the plywood should hang slightly over the edges of the end dowels. Using 1-inch screws, screw the side edges of the plywood down onto each dowel, approximately 1/2 inch from the side boards.
Place the corrugated tin over the plywood, trimming the ends of the tin with tin snips so that any sharp edges lie flush against the wood in order to prevent cuts to the hands when using the washboard.
Drive screws in between the ribs (into the deeper recesses) of the tin just as you did with the plywood. Use two screws every 4 inches, making sure they are screwed in until flush with the metal surface to prevent snagging of laundry when the washboard is in use.