Generally speaking, you are engaging in Jail Solidarity when you are in custody of police or jail guards and are using the Jail Solidarity non-cooperation tactics like those described above (going limp, etc.). Your actions in Jail Solidarity directly affect the police, jail guards, and jail administration.
Though one of the most visible and potentially empowering aspects of Legal Solidarity is physical noncooperation in custody, non-cooperation is not done for its own sake. Always use non-cooperation or acts of resistance to take care of each other.
Brutality at the hands of police and guards has occurred and is dangerous. By using non-cooperation tactics, you risk aggravating police and guards. Activists can really get hurt. In addition, physical noncooperation (e.g. going limp) could result in charges of resisting an officer.
Non-cooperation need not be just physical. One tactic typically associated with Jail Solidarity is withholding your names upon arrest. The police usually won't release people who they can't find again.
Some activist groups that have been in jail and nameless have found that they: stay together; clog the jails; can keep known organisers and legally vulnerable people from being targeted for mistreatment or more severe charges; make the paperwork hard; and appear to the jails, prosecutor and media as one unified group. Keeping a committed group in the jails until demands are met is central to the tactics of Jail Solidarity.