X-PLOR provides the possibility of refinement of several rigid groups (see Section 9.2). The following example file is an application to crystallographic refinement. Parts of the molecule that are not specified in any GROUp statement remain fixed. The constraints fix statement has no influence on rigid-body refinement. In the following example, the orientational and translational parameters of two domains (residues 1--30 and 31--70) of the molecule are refined: