1. Make two lists of Wood.
Each 500mm long
The lists needs to be completely straight and even. Make sure they are witout twigs in the material.
These lists of wood may become one of your most important tools in your workshop.
2. Position the lists
Lay the lists opposite of the direction of the wood in your piece. One at each end. This will provide you with two reference points.
Take a couple of steps back and aim. The two lists should appear parallel, if they do then the piece is straight. Congratulations! This is what you want. Unfortunately that is not always the case – If it`s not straight move on to step 4.
4. Mark it
If the wood is not straight take a pencile and mark where the wood is elevated. Then scrubb down. An important note though, do not remvoe too much at a time. better to go slowly then to end up having the hole piece renderd useless due to beeing in a hurry.
The last and most important step is to re-check. Repeat step 3-5 until you are completely satisfied.
When it is straight mark the side so you know that side is straight turn the piece and do the hole process on the other side.