Abstract: A unitary, light-tight, self-locking, flip-top package, for securely containing light-sensitive material, which comprises (1) a closable and openable rectanguloid box having bottom, front, rear, and opposite end walls and (2) a mating lid having a top wall movably connected to the box rear wall, with front and opposite end walls depending therefrom in close confronting relation to the corresponding box walls. The box and lid walls are all formed from a single paperboard blank that is specially configured with various panels, flaps, and tabs adapted to be readily folded into close interlocking relationships, to provide a unitary, light-tight, flip-top package which can also be readily unfolded and stored in flat condition for reuse.