For normal use, keep a “sacrificial” 2x4 in the slot. When it gets too “kerfed up,” flip it over and use the opposite edge until it’s time to replace the whole thing. Drop a longer 2x4 into the channel to support bigger projects. Change working heights by simply slipping a different-size board—a 2x4, 2x6, 2x8, 2x10 or 2x12—into the channel.