Noun
leadline (plural leadlines)
A leash or strap for leading an animal.
A sounding line; an instrument used in navigation to measure water depth.
(fishing) A weighted line for holding down the lower edge of a gillnet.
Source: en.wiktionary.orgThe horse show included Halter classes, Showmanship, English and Western Classes, Trail, Open Costume Class, Leadline and Walk/Trot, Driving Classes, and Gymkhana. Source: Internet