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In order to keep the blades from going all the way through or if it's necessary to tilt the holder to see what you're looking for make a third 2x4 to match the other two. Using a half lap joint, cut an additional 1x4 and extend this to the third 2x4. With the extended "case" blades are kept secure. And for mobility add a handle to the top and now it's portable, you can carry the entire selection to the table saw, radial arm saw, etc.