Stiff behavior may be specified for any Link degree-of-freedom (DOF) by selecting either the Fixed Behavior option, or by assigning a reasonably large stiffness value, as described in the Rigid behavior article. The Fixed Behavior option is convenient for simulating either a support restraint or a constraint between two joints. In general, however, a link with fixed DOF should not be directly connected to other objects with fixed DOF, or to joints within a constraint condition. In such cases, we recommend using sufficiently large stiffness values on the order of 1e11 kN-m (or kN-m/rad). Large stiffness values should also be used when forces must be reported for the fixed/stiff DOF, and when adding or removing links during Staged construction.