The materials and procedures of the 19th-century lithographer are duplicated in almost every respect by the contemporary hand printer. An image is drawn with tusche (a carbon pigment in liquid form) and litho crayon before the printing surface is fixed, moistened, and inked in preparation for printing. The printing itself is done on a press that exerts a sliding or scraping pressure.
The dream about keys is a dream that refers to solutions to one's life problems. The question you have to ask yourself when you have this type of dream is 'what is the problem I have today that needs a solution, or a key? (read all at source)
To see an opened door in your dream symbolizes your receptiveness and willingness to accept new ideas/concepts. In particular, to see a light behind the door suggests that you are moving toward greater enlightenment/spirituality. To dream that the door is closed or locked signifies opportunities that are denied and not available to you or that you have missed out on. Something or someone is blocking your progress.