singletree

/S IH1 NG G AH0 L T R IY0/
noun
  1. 1

    A bar behind draft animals and in front of a load, such as a wagon, that balances the load. Generally the animals are attached at the ends and the wagon or other load to a pivot in the middle of the singletree.

Source: https://en.wiktionary.org/wiki/singletree