ground-plate

from The Century Dictionary.

• noun In building, the lowest horizontal timber of a frame, which receives the other timbers of a wooden erection; the groundsill.
• noun In railway engin., a bed-plate used under sleepers or ties in some kinds of ground.
• noun An earth-plate or piece of metal sunk in the ground to form the connection “to earth” from a telegraph-wire. Gas- or water-mains are often made to serve as ground-plates.