piling : Idioms & Phrases

• sheet piles connected together at the edges by dovetailed tongues and grooves.

Webster 1913

• noun a pile in a row of piles driven side by side to retain earth or prevent seepage
  sheath pile; sheet pile.
  

WordNet

• a series of piles made of planks or half logs driven edge to edge, used to form the walls of cofferdams, etc.

Webster 1913