groundline

noun3

1. •
   A line drawn to signify the surface of the ground, especially in architectural blueprints and in drawings by children which lack dimension.
2. •
   A weighted fishing line that lies along the floor of the body of water in which the user is fishing.
3. •
   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.