Abstract: A sieve frame of the kind generally used in a sifter where a number of such frames are superimposed in a stack, the frame comprising side walls (13) adapted to enclose a loose clothing frame through which the material is sifted, being made from a food-quality plastics material and having male and female interlocking labyrinth seals (20, 21, 22 and 23, 24, 25) at the upper and lower edges to lock the superimposed frames together and to seal against the escape of stock between the frames.