Helical piles are a factory-manufactured steel foundation system consisting of a central shaft with one or more helix-shaped bearing plates, normally referred to as blades or flights, welded to the lead section. Extension shafts, with or without additional helix blades, are used to extend the pile to competent load-bearing soils and to achieve design depth and capacity. Brackets are used at the tops of the piles for attachment to structures, either for new construction or retrofit applications. Helical piles are advanced (screwed) into the ground wi th the application of torque. The terms helical piles, screw piles, helical piers, helical anchors, helix piers, and helix anchors are often used interchangeably by specifiers. However, the term 'pier' more often refers to a helical pile loaded in axial compression, while the term 'anchor' more often refers to a helical pile loaded in axial tension.