In practice, letterpress also includes other forms of relief printing with printing presses, such as wood engravings, photo-etched zinc "cuts" (plates), and linoleum blocks, which can be used alongside metal type, or wood type in a single operation, as well as stereotypes and electrotypes of type and blocks. With certain letterpress units, it is also possible to join movable type with slugs cast using hot metal typesetting. In theory, anything that is "type high" and so forms a layer exactly 0.918 in. thick between the bed and the paper can be printed using letterpress.