Abstract: Method and slide-casting machine for the casting of hollow precast units of concrete by means of slide-casting. Concrete mix is extruded onto a base by using one or several shaping members that form a cavity and the mix is compacted by moving the shaping members. The outer face of the shaping members is provided with a projection or projections, or a projection or projections are formed at the outer face of the shaping members from time to time. The locations of the projections are changed to the longitudinal axis of the shaping members. Thereby the shaping members produce forces compressing the mix in the surrounding mix, i.e. forces that compact the concrete. It is possible to use shaping members in which the shape of the mantle portion can be changed so that the distances of the different points at the outer face of the shaping member from the longitudinal axis of the shaping member vary.