The parameter library is used by the MAKE_RESTRAINTS command to construct bond, angle, dihedral angle, improper dihedral angle, and non-bonded Lennard-Jones restraints. If some parameters for these restraints are missing, they are guessed on the fly from the current Cartesian coordinates of the MODEL. Thus, when there are missing parameters, the MODEL coordinates must be defined before calling MAKE_RESTRAINTS. The coordinates can be defined by the BUILD_MODEL command (from the IC entries in the residue topology library), by the READ_MODEL command (from an existing coordinate file for MODEL), or by the TRANSFER_XYZ command (from template coordinate files aligned with MODEL). The bonds, angles, and improper dihedral angles are restrained by a harmonic potential with the mean equal to the value in the current structure and a force constant typical for chemical bonds, angles, and improper dihedral angles, respectively. The dihedral angles are restrained by a tri-modal cosine term with the mean equal to the angle in the current structure. A message detailing MODELLER's improvization is written to the log file.