A crossbar in front of a wagon with a swingletree at each end, enabling two horses to be harnessed.
- ‘The doubletree on the wagon could be adjusted to allow one horse to pull more.’
- ‘The wheel horses pull on the doubletree against this hammerpin running through the wagon-tonque.’
Mid 19th century: from double, on the pattern of singletree.
We take a look at several popular, though confusing, punctuation marks.