According to the invention, an actuator is provided for a milking installation, wherein the actuator is fixed at a distance to a teat cup cluster and is mechanically coupled to the teat cup cluster via a flexible component so as to incite a stimulating movement of the teat cup cluster on the udder by means of an actuator element. The inventive actuator can also be used to adjust the angle of tilt of the teat cup cluster during milking. The invention also provides a retaining device for teat cups, comprising a fastening device for fixing the retaining device on a predetermined milking position, wherein the retaining device is furthermore formed to maintain, during a first operational phase, every teat cup of a plurality of teat cups in a fixed position relative to each other and to allow manual access to every retained teat cup in such a manner that during a second operational phase every teat cup can be manually moved in several directions relative to the retaining device and at least one additional teat cup.