The 2s, 3s, and 4s of Surfacing
Wood is an organic material, so not every piece is going to be perfect. And that's ok. Many small imperfections can be worked out during milling. Here's what you need to know:
S2S---Surface 2 Sides---This is a planing pass, top, and bottom. Usually, after running a 4/4 board S2S, it will come in at a smooth 3/4" thick (but still needs sanding). S2S can also take a board down to almost any thickness required. The sides of the board will still be rough and need additional milling to be suitable for most projects.
S3S----Surface 3 Sides---After running a b
oard S2S, the board is joined on one edge to make it straight. This creates three surfaced sides. You'll need to rip the board to your desired width, and possibly add a joined edge to create a board that is smooth on all four sides.
S4S-----Surface 4 Sides---Just like S3S, then the board is ripped to width on the fourth edge and then joined for a smooth edge. A board that is finished on all four sides is ready to taken on any project, including glue ups.
Don't have a surface planer or jointer? Check with your local hardwood retailer. They may offer these services for a small fee. And even if you have the right equipment in your shop, you may want to take advantage of these services to get a jump start on your next project.