text: To place the sample under investigation into the x-ray beam, a sample holder is required. While in white-beam techniques a simple fixed holder is sometimes sufficient, experiments with monochromatic techniques typically require one or more degrees of freedom of rotational motion. Samples are therefore placed on a diffractometer, allowing to orient the sample along one, two or three axes. If the sample needs to be displaced, e.g. in order to scan its surface through the beam in several steps, additional translational degrees of freedom are required.