double curtain rod 
Rod composed of two single rods, used to hang two curtains in front of the same window.
single curtain rod 
Rectangular metal bar composed of two parts: one is inserted into the other in order to adjust the length.
curtain pole 
Ornamental cylindrical rod, made of wood or metal; it supports a curtain that is opened by hand.
eyelet 
Small metal ring into which a hook is inserted to support a curtain.