two parts are designated at 50a and 52a the light trap construction along the ends of the cassette is the same as that described along the sides fig5 illustrates the light construction along one edge the parts being designated 50b and 52b the parts of the light trap may be constructed as continuous strips along the sides and ends or these parts can be constructed as single continuous strips extending all the way around the cassette along both sides and ends as illustrated in fig5 the ends of the cassette are closed only by the male and female parts of the light trap numeral 60 designates a pad which preferably may be foam rubber or plastic although a pad of felt may be used which is cemented to the obverse or underside of the back by glue as designated at 61 in fig5 its purpose is to hold the film in close contact with the obverse side of the front numeral 64 designates an air hole which serves to relieve the pressure of the air when opening or closing the holder the size of the hole or holes vary with the size of the cassette holder fig6 and 7 show a modified form of.