If you want to make sure that the angles on your board are parallel, then one way of doing this is to use an electronic level. Looking very much like the hand-held variety, these electronic tools take some of the strain and effort out of using a spirit level, and also give you precise readings. In order to use the electronic level correctly, you will have to learn how to manage the digitized tool.
Step 1 - Clearing the Level
Before you can begin measuring, you need to make sure that your level is working correctly, and then clear it of any memorized details. Some electronic level tools can be set to remember a certain position, and this can make using them on a new item very difficult. Set the level on a flat surface, such as a table, and ensure that all the dials are pointing to "0". Press the "Reset" button if you cannot get 00.0 to begin with.
Step 2 - Using the Level
Take your level, and place it against the side of the board that you wish to check. You should hold the electronic level against the board until the electronic display gives you a reading. This will be the angle of your board.