both the tongue cutting blades on the bit and simply raise it up high enough so the upper most cutter will not come into contact with any of the wood. By doing this, the bottom tongue-cutting blade cuts the rabbet on the bottom edge of the stock while the second blade spins harmlessly in mid-air leaving a strip of wood between the two of them. Just like with milling the cove cuts, it is a good idea to run all of the new siding through the rabbet process in a consecutive manner so they all have the same alignment. Weatherboard siding is designed to function by each piece overlapping the piece below it. The rabbet on one piece will overlap the cove cut on the piece immediately below it. The overlap is what keeps water from getting between the boards. This is why it is important for all of the boards to have a uniform alignment.
Milling #105 weatherboard siding out of pressure-treated lumber is a simple process and only requires a router and a cou- ple of specialized bits that can later be used on other projects. I milled the 34 linear feet that I needed in less than three hours start to finish. Three hours of my time is a small investment for sid- ing that will be rot-resistant for years to come (with proper priming and painting). If you own a home that as any kind of wooden siding, and especially an older home that has weatherboard siding, consider installing your own custom-milled treated siding on those couple of places that always seem to stay wet.
Remove all damaged siding down to the bare studs. Conditioned spaces will require require insula- tion, sheathing and house wrap.
The interlocking siding begins at the top. Install with siding nails then finish with primer and exterior-grade paint.