We have a brass Light Extension Rod, vintage item.  It is fairly ornate with a finial on the base which unscrews and then the top portion is molded with some beading along the top under the portion which is threaded.  It measures about 15 1/4" with the finial being about 2 1/2" of that, the plain brass rod measures about 10 1/4" and the top being the balance.  The top threaded base is about 1 1/8" across the opening with the beaded portion being about 1 1/4" across.  This piece is tarnished but very pretty.  There is no place for wires - I "believe" the top piece went into something and after unscrewing the finial the light piece would go on being held in place by the finial......