PURPOSE: To reinforce a lip for forming a slit and to ensure the light eliminating capacity by integrally forming bars with a housing, as for a cassette for holding photoreceptive web material.

CONSTITUTION: In the case of injection-molding half outer shells 2 and 3 made of synthetic resin, the bars 27 and 30 are integrally molded. Then the half outer shells 2 and 3 are bonded along a joint line 4. The recessed lip 9 is bonded with an intermediate wall part 10 through a curved end edge 25 and a bend 26, then, the lip is reinforced in the axial direction, and also, the lip is reinforced by the bar 27 in the longitudinal and horizontal directions Also, the projecting lip 15 is bonded with an intermediate wall part 16, then, the deformation generated at pulling out a roll 24 is surely prevented by the bar 30. By such a configuration the lip is reinforced, so that the light is surely eliminated.