Abstract: A rotary screen appliance for the sifting of sand at a construction site is fittable directly to the mouth of a motorized driving device such as a cement mixer. A dismantable screen cage is connected to an armature preferably having three guide arms. A fastening portion is slidably attached to each guide arm and extends at an acute angle therefrom such that the fastening portions may engage the mouth of a cement mixer and thereby lock the screen cage thereto. Rotation of the cement mixer causes rotation of the screen cage. A device for rapping on the screen cage and thereby shaking it as it rotates is also provided.