Your deadbolt is the only lock on your front door doing real work. The knob or lever above it can be defeated with a firm shoulder, but a healthy deadbolt sinks a full inch of solid steel into the frame. The catch: most homes were built with the cheapest deadbolt the contractor could buy, and most homeowners have never once tested theirs. If your key is getting harder to turn, that’s not just an annoyance. It’s often the first of the signs your deadbolt needs replacing, and i