Sorry to butt in here, but, pin? pin = metal? Metal + water = rust? Rust = bad news (pollution) for aquariums?
And aren't cork boards treated with chemicals (like paint, for instance)? Shouldn't it be sterilized or cleaned in some way?
I too agree cork board is way cool for a moss background. Another idea I've heard is to use the little plastic suction cup thingies that come with some airline hose packets. Clip the little moss bundles to those.