A rope or chain used to tie, especially an animal, to a post or other fixed place, usually so that it can move freely without a small area. (Cambridge Dictionary)
A line (as of rope or chain) by which an animal is fastened so as to restrict its range of movement. (Merriam – Webster)
A tether is a rope or chain which is used to tie an animal to a post or fence so that it can only move around within a small area. (Collins Dictionary)
Triggers and tethers.