-17 of this instrument to manage prisoners who have caused, or are judged likely to cause, serious harm to others, or who present a very serious risk to the safety or security of the prison. The second chapter is a collection of international standards on solitary confinement such as the Mandela Rules (SMR), the European Prison Rules (EPR) and other standards set by international human rights bodies. The standards are divided by theme, available to the NPMs to monitor isolation in their own country, and develop their own standards adapting them to the national context in which they operate. These soft law tools are not binding for the State authorities, but they mark the direction to follow, and are objectives to pursue in the path towards change of which the NPM can be an important actor. The contents of the third chapter are a practical guide to monitor isolation. They are based on good practices emerging from the interviews, and meetings with NPMs and experts, with particular attention to physical visits to the penitentiary institute. It is divided into phases (preparation of the visit, carrying out of the visits, follow-up) and, like the other chapters, into thematic chapters (study of prison registers, role of doctors, interviews, material conditions, etc.). Monitoring Solitary Confinement in Prison