Correspondence filing cassette unit - has sides with openings snapping into engagement with tongues between top flange walls

摘要

The correspondence filing cassette is made from a sheet of material with two sides folded upwards, and joined together by the base, and a separate U-section plastic top whose height is at the most equal to that of the vertical sides. Both flanges (22) at right angles to the main body (21) of the top (20) are formed by two flange walls (23,24), spaced apart for the same distance as the thickness of the sides. The inner flange walls (23) each have a spring tongue (25) bent towards the outer one, and which snaps into engagement with an opening formed in the side (12) when this is thrust between the flange walls.