I used a lawyer's stacking book case for my handgun storage. I liked it because it matched my roll top desk. To protect the guns, I placed cakes of camphor with a corner torn on their covering. At that time I could buy cakes of camphor at the drug store. I don't know if you still can. I noticed that the toolmakers at work used camphor cakes in their drawers with steel gages to keep them from rusting. As an alternative, you could buy (or build) display cases and install damp chasers like they sell for safes or pianos. If you use dowels, I would put a finish on them. Maybe boiled linseed oil or Tung oil. I wouldn't mount a display case directly on an exterior wall. If you want to do that I would put in spacers to stand out from the wall and allow some air movement behind.

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Luke 22:36