The distinguishing trait of all lap steels is that the strings are raised at both the nut and bridge by about half an inch. This makes the frets unusable (the instrument is played with a slide) and in fact, some models simply substitute markers to aid the player in correctly voicing notes and chords. Early on, such instruments were called Hawaiian guitars, as there is an instrument that has been long used in Hawaiian music (at least since 1800 or earlier) that works on the same principle. Such instruments were hugely popular in the U.S. during the 1920s and 1930s. Lap steels in general, and electric lap steels in particular, incorporates the entire neck into the body of the guitar, allowing for higher notes to be played than would be possible on a standard electric.