If we're trying to keep people out on the street for an extended action, we might want to take opportunities to get quickly released from custody. Or if we are asked to make unacceptable compromises in order to be released, for example, posting high bail or accepting conditions that might prevent us from doing future actions, we ma y need to use in-jail solidarity. The authorities may also ask people to sign statements saying they will not return to a certain action or area. To stay in jail, refuse to sign or to post bail. Bail is one of the ways the poor are kept incarcerated and people with money get released.
Some activists refuse to post bail as part of their moral or political stand.
For others, the choice may depend upon the situation. For this tactic to be effective, protestors should not carry identification to the action. For this reason, it needs to be coordinated ahead of time. This tactic also greatly interferes with the smooth running of the jail system, and is a tactic generally hated by the authorities. It can be a powerful bargaining point in solidarity negotiations.