A monodirectional or bi-directional distributor plate for crossflow cassette-type filtration appliances is provided which comprises three parts and is used in the ultrafiltration or microfiltration of liquids. The three-part distributor plate assembly comprises a middle plate member, an upper plate member and a lower plate member, which when combined has a front and rear surface, a first and second side wall and a first and second edge wall. The front and rear surfaces of the distributor plate assembly are provided with feed, residue and filtrate orifices arranged to communicate with feed, residue and filtrate orifices of a plurality of filter cassettes. Due to the manner of flow to and/or from associated filter cassettes by way of the three-part distributor plate assembly, equal pressure can be achieved at all orifices to ensure equal flow over a filter membrane surface increasing filtration performance. The three-part construction of the distributor plate allows for easy adaptability to various installations.