Abstract: In a housing for co-rotational twin screw machine for longitudinally conveying non-free flowing materials, the housing having two intersecting cyclindrical bores for receiving two intermeshing screws and means forming at least one port thereover, the improvement wherein the means forms an anti-bridging port comprising one planar longitudinal side wall having the lower edge thereof disposed adjacent the intersecting area of the two bores and wherein the sidewall slopes outwardly from the lower edge above one bore at about 60.degree. to 90.degree. with respect to the horizontal plane and extends approximately tangentially with respect to said one bore.