How to lubricate entry doors and what to use : Graphite Powder
Quote from Article entitled How to lubricate entry doors and what to use:
In general, many modern locking-mechanisms rarely need to be oiled. But if the door lock does need some maintenance, you should use only special compounds, since badly-chosen products can eventually make the mechanism inoperable. In any case, everything that is required for maintaining a lock should be noted in the instructions.
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