Can you be more specific ? Type of fixture & model number ? If I did this installation: UF cable directly buried, conductor type would be solid. PVC conduit, cable type could be either solid or stranded. I would use stranded myself.
520.65 Festoons. Joints in festoon wiring shall be staggered.
Where such lampholders have terminals of a type that puncture
the insulation and make contact with the conductors, they
shall be attached only to conductors of the stranded type.
Lamps enclosed in lanterns or similar devices of combustible
material shall be equipped with guards.