Marking the Second Knifewall

With the first wall cut made, you can now mark the second wall straight from the shelf/divider piece to get a perfect fit. Take your corresponding piece of wood and push it up tight against the wall you have just cut. The width should be close to the pencil line, but that only served as a rough guideline. Only the knife will create an exact, defining wall. Make a small knife nick right up against the second piece, almost as if trying to reach underneath it. This way, you can be sure you won’t end up with a loose joint.

Now put the divider piece aside, making sure you’ve identified the knife nick. Turn your piece around for convenience and register your square against the tip of the knife locked inside the nick you just made. Again, remember the square must be placed so that you’re cutting on the waste side of the line, i.e. inside the recess. With the square locked in place, make a faint knifewall across the board and then go again a little deeper. When you’re sure you’re deep enough that the knife won’t drift, go with a third pass more heavily. This will make it easier to pare cut on the waste side before cutting down the rest of the wall.

If you have more than one housing dado to cut, mark each piece and its corresponding recess with letters or numbers. This is especially important when using hand planed stock, as there can always be minor discrepancies.