Bob and wheel is the common name for a metrical device most famously used by the Pearl Poet in Sir Gawain and the Green Knight. The feature is found mainly in Middle English and Middle Scots poetry, where the bob and wheel occur typically at the end of a stanza. The "bob" is a very short line, sometimes of only two syllables, followed by the "wheel," longer lines with internal rhyme. There are at least forty known examples of bob and wheel use, but the origin of the form is obscure. It seems to predate the Pearl Poet. Bob and wheel is not used often in modern poetry.
The Pearl Poet uses the bob and wheel as a transition or pivot between his alliterative verse and a summary/counterpoint rhyming verse, as in this example from the first stanza of the poem:
"On mony bonkkes ful brode Bretayn he settes with wynne,The "with wynne" is an alliterative "bob," and the rhyming "wheel" (which summarizes the action) follows in the next four lines.
The matter of the bob and wheel varies, but, generally, it functions as a refrain or, at least as often, a summary or ironic counterpoint to the stanza that preceded it. Both the Anglo-Saxon use of litotes and the French-inspired refrain show up in the bob and wheel.
Some Modern English poets and contemporary poets have revived the use of the bob and wheel. Because of the Pearl Poet's use of the bob and wheel, numerous contemporary critical discussions treat it as a wholly regular metrical form (suggesting that it is always as the Pearl Poet uses it). In fact, in Middle English, there is great variation.