not sure hyow you use one, u just stick it in your soundhole (i think you may have to fill it up wth water) [the instructiosn will guide you] the only reason you'll need a humidifier is if you live in a dry climate or you move from wet to dry climate. i use a dehimidifier in my whoel hosue, so i have plenty of humidity to spare if you want it
I only put one in my case. I take a sponge with water that I put in alittle case, on which I drill a couple hole. Tadah!
lol ^ nice
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It is worth it if you have an all solid wood guitar. It won't matter with laminate. It will just protect the guitar from cracking at the seam and keeps it looking nicer. There are some good videos about it on taylor guitar's website.