Kreg Tool Tip: Choose the Correct Kreg Screw Length. The first step is to make sure you are using the correct screw-thread type. Fine-thread screws are recommended for hardwoods (like cherry, maple, oak, etc), while coarse-thread screws are the preferred choice for softwoods (like cedar, pine, etc). Selecting the correct length is easy; it’s based on the thickness of your material. The chart below will help you select the correct screw length for your next project.