34 which surround the wall 7 of the housing 1 the surfaces of the wall 33 the side walls 35 36 and the closure end 37 are lined on the inside with the polytetrafluoroethylene based anti adhesion coating 21 in accordance with the invention the side walls 35 36 have chambers 38 39 which are likewise coated as in the preceding embodiment they serve to avert sharp edges and shoulders at which trash could settle the side walls 35 and 36 have blind bores 40 and 41 on their outside as in the preceding embodiment these bores serve the purpose of fixation of the insert by means of screws which are installed through the side walls of the housing 1 fig8 shows a preferred embodiment in which the insert 42 is in the form of a chute 43 formed of thin metal sheet material each of the four walls of the chute of which only the three walls 44 45 46 can be seen is provided on its interior surface with the coating 21 of polytetrafluoroethylene material this insert can be fitted in the trash discharge passage 3 of existing opening devices the fixation is done very simply by flanging over the wall 46 at.