The Insulator Spindle No.4 has a standard ⅝ thread for a single insulator the other end threaded to allow it to be bolted through a pole arm or wall bracket. Used in pairs in a 
Bracket No.2 (wall), 
Bracket No.14 (eves) for open wires. Seen here mounted on a 
wall spike, this arrangement is commonly used for terminating a dropwire as its not suitable for open wires.