Bob and wheel is a pairing of two metrical schemes. The wheel is a type of rhythm used in hymns or narrative songs sung in European churches or gatherings from the 12th to the 16th Centuries. A wheel occurs when at the end of each stanza, the song and the lyric return to some peculiar rhythm. In some instances the wheel is a return to something that resembles no definable poetic rhythm. A bob is a very short line, often two assertive syllables that announces the start of the wheel.