groundline

Noun

 * 1)  A line drawn to signify the surface of the ground, especially in architectural blueprints and in drawings by children which lack dimension.
 * 2) In equestrian show jumping, a marker such as a row of flowers which signifies the point from which a horse should begin a jump over an obstacle.
 * 3)  A weighted fishing line that lies along the floor of the body of water in which the user is fishing.