I built this rack to organize my spade bits in one convenient location. A "VEE" can be cut in the top with a router (or a tilted table saw) so that the bits all rest in one plane, making it easy to see the sizes. It also keeps them in line so you could add additional back layers to accept more bits or screw drivers, etc.
Step 1: Expand Your Rack by Adding Layers.
You could expand your storage by adding layers for more bits, screw drivers or other tools. The drawing shows additional layers set up with a "VEE" groove but it could be left with a flat top, depending upon how you might want to use it.