You will need
  • -some tap water;
  • aerosol penetrating lubricant for locks;
  • -a bit of sunflower oil.
Insert the key into the keyhole and try to turn it slightly clockwise and counterclockwise, without resorting to force. While holding the lock arm, lock it in a fixed position. If it does not give any results, do not attempt to repeatedly repeat the same motion, increasing strength and intensity of pressure, without AIDS you are unlikely something will achieve.
Enter to start with the plain tap water in a spare container and pour on the "naughty" castle. If it happens in the cold season, rain water, stiff it just might freeze under the influence of the coming frost, bound thereby the lock mechanism. Better if the water will be hot, but rather can be plain water from the tap, you can quickly dial in your house or apartment.
Use spray lubricant, if after thawing the hanging castle is refusing to come to any compromise with you. Direct the tube through which lubricant is supplied, in its bore, and press on the spray can. The effect of this must follow immediately - even old and heavily rusted locks quickly "come alive" after processing them with penetrating lubricant.
Do not despair if at the right moment specialized lubricant for locks in your house was not there. To perform its function, though perhaps not as efficiently, maybe sunflower oil. Carefully pour a small amount into the keyhole and try to open the "naughty" castle again. It is possible that you it is easy to manage, and to resort to grinders left on the most extreme case, still do not have.