Step 1: Assemble the Toolbox
Then you add a humidity absorber, the types that have a plastic collection tub. You remove the seal of course ;-)
Put all the tools that you what to keep away from humidity in the box. Close it and you are done. Give it a few hours for the humidity to go down.
OPTIONAL: I bought a hygrometer (humidity meter) off ebay for a few dollars just to make sure the concept was actually working. The humidity levels in the box are usually kept in the low 20% down from the ambient tropical 80+%!
I have been using this box for over a year now and the tools remain rust free! Because the volume of the box is small and the box is sealed , the humidity absorber lasts a long time. I've not changed mine yet. I have made several other boxes. This can also be used for photography equipment or any other stuff that needs to stay away from humidity.