You use your dead bolt every day without giving a thought to maintenance. But one of these days, it's going to fight back and refuse to open. Don't panic; it's just crying for a few shots of lube. You can get it working again with dry Teflon lube spray. It's a better choice than graphite because it sprays on wet to soak into the lock mechanism. The solvent evaporates, leaving behind a dry, slippery powder. Start by lubing the lock cylinder (Photo 1).
If lubing the lock cylinder doesn't free it, you'll need to lube the bolt mechanism (Photo 2).