The ox tether is used for stone delivery. It is very cheap to build, yet essential to ferry stone to the stockpile, which can be used then for constructions and siting defensive buildings.
A goadsmen is needed to operate this building, who leads the ox to its destination and loads it with stone blocks from the quarry. The ox will start stone delivery when 8 blocks are loaded.
It is imperative to build multiple tethers in order to ensure constant delivery so that the quarry's stockpile will not get full.