Square Lumber Without a Jointer: Four Methods

Put a rough sawn board on a flat bench and one corner lifts. Push that corner down and a different one rises. That is twist, and it is the reason a board cannot be squared by running it through a thickness planer: the planer presses the board flat against its bed, shaves the top, and lets the board spring back into the same shape it started in, only thinner. A jointer solves that by referencing a face against a long flat table. Four other things solve it too, and which one you should use depends less on the board than on which machines are already in your shop.

Flatten one face with a planer sled, a router sled or a hand plane, then make one edge straight on a table saw with a straight-line rip jig or with a hand plane. From those two reference surfaces the planer and the saw finish the second face and second edge. The tool you own decides the method; the order of operations is the same in all four.

• A planer on its own makes a board thinner, not flatter. It copies the shape it is given.
• Flatten a face first. Every later cut references that face, so an error there follows the board through.
• Own a thickness planer: build a planer sled. It is the fastest of the four and handles twist well.
• Own a table saw but no planer: a straight-line rip jig gives a jointed edge, and a hand plane does the faces.
• Own a router: a router sled flattens boards wider than any home shop planer will take.
• Own neither machine: a jack plane and winding sticks do all of it, and did for centuries.
• Check with winding sticks before and after. A board that is not in twist rarely needs the sled at all.

Pick the Method by the Tools You Already Own

In short: the four methods are not ranked best to worst, they are sorted by what is on your bench.

Most guides to this problem present a favorite technique and assume you have the machine it needs. In practice the question is narrower than that. You have some subset of a planer, a table saw, a router and a set of hand planes, and the useful answer is which of those gets you to a square board.

One thing worth settling before you buy anything else: if the choice is between a jointer and a thickness planer, the planer is the more useful machine. A planer with a sled will do the jointer's job slowly, while a jointer on its own cannot bring a board to a consistent thickness at all. That ordering is part of the wider buying sequence in our woodworking machinery guide, and the small-shop version of the same question is covered in budget tools for small spaces.

The Order of Operations, Which Matters More Than the Method

In short: face, edge, second face, second edge, then ends. Each step uses the surface made in the step before.

This is the part that gets left implicit, and it is where most attempts go wrong. Squaring a board is not four independent operations. It is a chain, and each link references the one before it. Skip a step or reorder two and the errors compound instead of cancelling.

1. Flatten one face. This is the reference surface for everything that follows. It does not need to be pretty, it needs to be flat and free of twist.
2. Straighten one edge, square to that face. The flattened face rides against the table or fence while this cut is made, which is what makes the edge square rather than merely straight.
3. Plane the second face parallel to the first. Now the thickness planer is the right tool, because it references the flat face against its bed and makes the top parallel to it. This is the step the planer is built for.
4. Rip the second edge parallel to the first. Jointed edge against the table saw fence, and the board comes out to width with two parallel edges.
5. Trim both ends square. A crosscut sled or a miter gauge, referencing a jointed edge.

Mill a little oversized and leave the board to sit for a day or two before the final passes if you can. Releasing the outer fibers of a rough board lets internal stress move, and a board milled to final dimension in one session will sometimes cup overnight. Wood movement is species dependent, and the seasonal behavior of common species is set out in the types of wood guide.

Method One: The Planer Sled

In short: a flat carrier that holds the board still in its twisted shape so the planer can cut a flat plane across it.

The sled is a flat, rigid platform that runs through the planer carrying the board on top of it. Shims under the board hold it in the position it wants to sit in, so the planer cuts a flat surface across the high spots instead of pressing the twist out and letting it return.

Build the sled from three quarter inch plywood or MDF, cut a couple of inches narrower than your planer's capacity and a foot longer than the boards you expect to flatten. Fix a stop at the trailing end so the board cannot slide backward under the pressure of the feed rollers, keeping the stop lower than the finished thickness you are aiming for.

To use it: set the board on the sled and rock it to find how it sits. Slide shims into every gap underneath until the board rests solid and does not rock at all. Playing cards, wood shims and folded paper all work. Fix the board to the sled with hot glue at the shims or with double-sided tape, take light passes of about a thirty-second of an inch, and stop when the top face is continuously clean with no rough sawn patches left. Then take the board off the sled, flip it, and run it through normally to bring the second face parallel.

The limit is width. A 13 inch planer with a sled in it will flatten a board of perhaps 11 inches, which covers most furniture stock and rules out wide tabletops and slabs.

Method Two: The Table Saw and a Straight-Line Rip Jig

In short: a flat carrier board with the workpiece fixed to it, run against the fence, produces a dead straight edge.

A table saw cannot flatten a face, but it makes an edge as straight as a jointer does, and for many projects that is the only half of the problem you have. The jig is a straight piece of plywood or MDF, longer than the boards you rip, with the rough board fixed on top of it so that the crooked edge overhangs.

Fix the board to the carrier with double-sided tape, screws through waste areas or toggle clamps. The amount of overhang does not matter. Run the carrier's own straight edge against the fence, and the blade cuts a straight line on the workpiece regardless of what its original edge was doing. Take the board off the carrier, put the newly straight edge against the fence, and rip the opposite edge parallel.

Two details make the difference. Use a ripping blade with fewer teeth, because a crosscut blade in a long rip burns and stalls. And keep the flattened face down on the table throughout, so that the edge comes out square to the face rather than square to nothing in particular.

Method Three: The Router Sled

In short: a router riding on rails above the board, taking overlapping passes, flattens anything that fits under it.

When the board is wider than the planer, the router sled is the answer. Two parallel rails sit either side of the board, shimmed level to each other, and a carriage holding the router bridges them. The router travels along the carriage and the carriage travels along the rails, so the bit sweeps a flat plane above whatever shape the board is in.

Shim the board underneath the same way you would on a planer sled, so it cannot rock. Use a bottom-cleaning or slab-flattening bit, which has a wide flat cutting face, and take shallow passes at about an eighth of an inch, overlapping each pass by roughly a third of the bit width. Flip and repeat, or switch to the planer for the second face once the first one is flat.

Slab flattening bits are large, often 2 inches across or more, and large bits have a low rated speed ceiling. Set the router accordingly before the first pass rather than after the first burn mark, using the figures in our router bit speed chart. The sled is the slowest of the four methods and it produces an extraordinary volume of chips, so it is worth doing outside or with serious dust extraction.

Method Four: Hand Planes

In short: scrub across the grain, jack diagonally, jointer along the length, checking with winding sticks throughout.

Hand planes did this work for several hundred years before machines existed, and for a single board they are often faster than building a jig. The sequence is three planes doing three different jobs, though a single well-set jack plane will do all of it more slowly.

Start by finding the high spots. Set the board on a flat bench, rock it, and pencil the corners that lift. Work across the grain with a scrub plane or a heavily cambered jack, taking the high corners down first. Cross-grain work removes material fast and leaves a rough surface, which is what you want at this stage. Move to a jack plane worked diagonally in both directions, which begins to true the surface, then finish along the grain with the longest plane you own. Length is what makes a plane flatten rather than follow: a long sole bridges the hollows and cuts only the peaks.

For the edge, clamp the board upright in a vise and work the long plane along the full length, checking square to the flattened face with a try square as you go. Correct a slight out-of-square by shifting the plane laterally on the edge so the camber of the iron takes more from the high side. The trade-offs between working this way and buying machines are laid out in hand tools versus power tools.

Checking Your Work With Winding Sticks

In short: two identical straight sticks, sighted across the board, make twist visible when your eye cannot see it directly.

Twist of a sixteenth of an inch over three feet is invisible to the naked eye and enough to rock a finished table. Winding sticks turn that small error into a large, obvious one.

Make a pair from any straight, stable stock, roughly 18 to 24 inches long, an inch or so tall, and identical to each other. Painting the top edge of one dark and putting a light stripe on the other makes them easier to read. Set one across the board at each end, crouch down at one end, and sight across the top edge of the near stick to the far one. Parallel means flat. If the far stick appears tilted relative to the near one, the board is in twist, and the direction of the tilt tells you which two corners are high.

Check before you start as well as after. Plenty of boards, especially shorter pieces cut from a longer one, have no meaningful twist and need only a straight edge rather than the full sequence. Cutting a long board into its rough project lengths before milling is the single easiest way to reduce how much flattening you have to do, because twist and bow both grow with length.

How Long a Board Can You Handle

In short: every one of these methods gets harder with length, and the fix is to cut to rough length first.

Length is the constraint nobody states. A planer sled needs infeed and outfeed support beyond its own length, and a sled much over six feet becomes unwieldy to shim and to feed. The table saw jig has the same problem in a different direction: a carrier board long enough for an eight foot plank needs support well past the front and back of the saw, and a wobble in that support shows up as a bow in the cut. Router sleds are limited by rail deflection, since rails sag in the middle under the weight of the carriage unless they are stiff or supported.

The practical answer for all four is the same. Cut your stock into rough project lengths with two or three inches of extra length on each piece before you flatten anything. Shorter pieces have less twist to remove, need less material taken off to reach flat, and turn an awkward eight foot operation into three easy ones.

Squaring Lumber FAQ

Can you square lumber with only a planer?

Yes, with a planer sled. A planer alone follows whatever shape the board already has and makes it thinner without making it flatter, so the sled is what turns a thickness planer into a face-flattening machine.

Do I need a jointer if I have a table saw?

No. A table saw with a straight-line rip jig produces a true edge that is as good as a jointed one. The table saw cannot flatten a cupped or twisted face, so pair it with a planer sled or a hand plane for the faces.

What is the correct order for squaring a board?

Flatten one face, then joint one edge square to that face, then plane the second face parallel to the first, then rip the second edge parallel to the first, then trim both ends square. Each step references a surface made in the step before it.

How do you check a board for twist?

Use winding sticks. Set two straight, identical sticks across the board at each end and sight along the top edges from one end. If they look parallel the face is flat, and if they cross the board is in twist.

Is a jointer worth buying for a small shop?

A thickness planer is the better first purchase. A planer with a sled can do the jointer's job slowly, while a jointer on its own cannot bring a board to a consistent thickness at all.