Secant pile walls are formed by constructing intersecting reinforced concrete piles. The secant piles are reinforced with either steel rebar or with steel beams and are constructed either by drilling under mud or by auger application. Primary piles are installed first with secondary (male) piles constructed in between primary (female) piles once the latter gain sufficient strength. Pile overlapping is typically in the order of 3 inches (8 cm). In a tangent pile wall, there is no pile overlapping as the piles are constructed flush to each other.