Woodcut—formally known as xylography—is a relief printing artistic technique in printmaking in which an image is carved into the surface of a block of wood, with the printing parts remaining level with the surface while the non-printing parts are removed, typically with gouges. The areas to show 'white' are cut away with a knife or chisel, leaving the characters or image to show in 'black' at the original surface level. The block is cut along the grain of the wood (unlike wood engraving where the block is cut in the end-grain). The surface is covered with ink by rolling over the surface with an ink-covered roller leaving ink upon the flat surface but not in the non-printing areas. Multiple colors can be printed by keying the paper to a frame around the woodblocks (where a different block is used for each color). The art of carving the woodcut can be called "xylography", but this is rarely used in English for images alone, although that and "xylographic" are used in connection with blockbooks, which are small books containing text and images in the same block. Single-leaf woodcut is a term for a woodcut presented as a single image or print, as opposed to a book illustration.