"Delta" bases are constructed from a series of interconnected triangles, also known as lattices, made of steel or aluminum. These systems are characterized as being wide at the base, then tapering from the bottom up to the mid-point of the structure.
The "delta" head assembly is installed to produce a supporting structure that extends up and out from the mid-point of the base. When installed, the structure angles outward, and creates a triangular shape that exhibits the structure's more colloquial name, "cat's head." The point of the structure is to elevate and "hang" the powerline arms.
The powerline arms "hang" and connect high-voltage wire conductors to subsequent lengths. These conductors are connected to the arms by what are referred to as "insulators." These components eliminate the chance of touching or "shorting" the wires against the steel or aluminum tower.