How to Straighten a Warped Piece of Wood

Set a twisted board on a flat work bench and determine the location of the twist and amount of twisting by laying the edge of a straightedge on the face and running it from one end of the board to the other. Mark the places where the wood humps with a pencil. Run a jack plane across the face diagonally to the grain to knock down the humps.

Inspect the board for cupping or crowning by laying the straightedge on the face of the board -- perpendicular to it -- and looking for gaps underneath, as you did while looking for twists. Cups and crowns produce humps that typically run the entire length of the board. Remove them by jack-planing parallel to the grain.

Straighten a bowed board by clamping it to a flat surface, such as a work bench. Before you do this, you need to replace some of the moisture on to the face that has shrunk, which is on the inside of the bow. One way to do this is to place the wood over a steaming pot of water for an hour. Another is to wrap it in wet towels and leave it overnight.

Clamp the bowed board by placing on the flat surface so that both ends touch the surface and the center is raised. Place a two-by-four across the center of the board.

Secure one end of the two-by-four tightly with a bar clamp, then place another bar clamp on the other end and use it to draw that end down and bring the center of the warped wood flush against the table. Leave the wood clamped until it dries.