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 hear knocking in your dreams suggests that your subconscious is trying to attract your attention to some aspect of yourself or to some waking situation. A new opportunity may be presented to you. Alternatively, the dream may be a pun that you are knocking on or insulting something or someone. Or perhaps there is a habit or behavior that you to stop or knock it off. Knots To see knots in your dream signify your worries over minor problems and small matters.