# The Flatten Hewn Shop Notes ยท https://hewn.build/shop-notes/the-flatten AI-drafted, not yet checked: Drafted by Chip, the writing system Hewn runs on Claude, from Hewn's craft corpus. Jonathan Salomons has not read this note yet, and no outside reader has checked it. Read it as a shop note: check a number before you cut to it. Cite as: "The Flatten." Hewn Shop Notes, hewn.build/shop-notes/the-flatten. Drafted 2026-04-22; AI-drafted, not yet checked. --- You pulled the clamps. The structure is solid. And the surfaces are wrong. One board sits a hair proud of its neighbor at the glue line. There's a ridge where a tenon shoulder meets the case side. End grain at the corners catches your fingernail when it shouldn't. None of this means you screwed up the glue-up. It means wood moved under clamp pressure, soaked up moisture from the glue, and shifted before it settled. That's what wood does. The flatten is where you deal with it. Before sanding. Before stain. Before any finish goes on. You cannot put a good finish on a bad surface. Everything downstream depends on what happens in the next twenty minutes. ## Diagnose first Don't pick up a plane until you know what's actually wrong. Lay winding sticks across the panel at opposite ends. Two parallel sticks of uniform thickness, scrap hardwood or machinist's rules, whatever's straight. Sight low across the near stick to the far one. If they're parallel, the panel is flat. If the far one tilts, you have twist. One diagonal pair of corners is high, the other is low. You cannot see twist by eye on a bare panel. You think you can, but you can't. The winding sticks make it obvious. Skip this step and you'll flatten the wrong spots, which creates new problems instead of solving old ones. Once twist is mapped, lay a straightedge along the grain in several positions across the width. You're looking for hollow (light under the center, rocking at the ends) and hump (light at the ends, contact at the middle). Now you know where to work. ## Match the tool to the problem **Stepped glue joints.** The card scraper is usually the right first move here. It cuts on the pull, stays close to the surface, and won't skip across the harder glue line the way a hand plane sometimes does. Work perpendicular to the joint first to bring the high side down, then switch to with-the-grain passes to clean the surface. A sharp scraper leaves a finish-ready surface without touching the surrounding wood. If the step is more than a millimeter or the panel has twist, start with the plane instead. **Twist in a solid panel.** Set a jack or a coarse #5 at 45 degrees to the grain and traverse the high corners. Light passes, one direction. Check winding sticks after every few passes. Once they read parallel, cross back the other way to even things out, then take finishing passes with the grain using a tight-mouthed #4. The jack does the work. The smoother closes the deal. **Ridges at joint intersections.** Proud tenon shoulders, pins that didn't get pared flush. Card scraper or chisel, directly on the ridge, nowhere else. You want to address the spot without removing material from the surrounding surface. Check with your fingertip. Flat means stop. **End grain proud at corners.** Block plane, in from the end. Not off the end, or you'll split the corner. Two or three light passes. Check with a fingertip and a straightedge laid across both surfaces. ## Final passes run with the grain Whatever tool you used to flatten, the last thing you do is run with the grain. Traversing cuts and cross-grain scraper work do the heavy lifting. They are not the finishing move. A few with-the-grain passes from a well-set smoother or a fresh scraper edge leave the surface ready for what comes next. Cross-grain scoring marks are invisible right now. Under an oil finish, they light up like neon. Don't find out the hard way. This is also why the random orbital sander, useful as it is, isn't the first answer here. An ROS removes material in a swirl pattern that doesn't follow the grain. Those swirls need a final hand-sand pass along the grain before any stain goes on, or they telegraph through the finish. On cherry, maple, or alder with a stained or reactive finish, this is not optional. On a painted surface, it doesn't matter. ## When you're done Four checks. Winding sticks read parallel. Straightedge shows no hollow or hump along the grain. Your hand, moved across the surface, catches nothing. Your fingernail, dragged across the glue line, finds no step. Pass all four and the surface is ready. Not perfect. Furniture is not a precision instrument. But a surface that clears these checks will take finish evenly, show the wood honestly, and not fight you at every step from here forward. The glue-up committed the structure. The flatten makes the surface true. Everything the finish does starts here.