How to lubricate entry doors and what to use : Graphite Powder
Quote from Article entitled How to lubricate entry doors and what to use:
Locks don't always need to be lubricated. For instance, if the lock works smoothly when the door is open, but the moment you shut it, the key hardly turns, then the problem isn't probably connected with the lock, but with the door. Most likely caved in or became twisted. Lock malfunction isn't often connected with a lack of oil! Sometimes its wear simply reaches a critical point. The lubrication of contact points can do well only in those parts of the lock where it is actually needed.
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