This is a combination wrench organizer designed for Craftsman brand metric wrenches from 7 mm to 22 mm. The design uses a 6mm laser cut plywood back board and a 6 piece printable rail to get the job done. I have included the Solid Works Source files for so that you can modify the design to suit your needs.

Build instructions

Download the 6 printable side rails and print them with high infill. I used PLA with 60% infill. If you build them as they are oriented they do not need support or a raft. Next download the back board files (dxf or pdf) use the files to cut out the back board. I used a laser because I had one handy. if you do not have a laser cutter handy download the Back Board .pdf and print it out at full scale. ( 156.13 mm by 208.62 mm) Glue the print out to your 6 mm (1/4 in) ply wood and use a jig saw, band saw or whatever is handy to cut out the back board.
Next try dry fitting all of the pieces and make sure every thing fits. If every thing fits ok this is the best time to clear coat the ply wood with some thing that will resist oil and water damage. I used some clear generic polyurethane. Finally you will want to glue the rails in place with marine goop, E-6000 or some sort of epoxy. I used marine goop because it is strong and flexible and it tends to hold up well over time. Apply a liberal amount of glue to the board and the printed part and press the printed part in place. The excess glue will squirt out of the round vent holes in the printed part. This lets you know you used enough glue and allows the printed parts to be pressed firmly against the wood. Allow the glue to dry completely and install your wrenches! 
Happy making.