This is a Doorstop Lamp and not a true Doorstop
This piece is always found with the U-Groove protruding from backside because
a Light Socket on a threaded stem is attached to the U shape Protrusion
via 2 nuts, one on each side of the U
For more information about Doorstop Lamps
See "1. DOORSTOP, LAMP or BOOKEND ?"
Under the DOORSTOP KNOWLEDGE
icon on the HOME PAGE of this site