small book

noun2

1. •
   (historical) Synonym of logbook.
2. •
   (no longer used) A process by which someone is to be detained or held on investigation without an official charge being filed; suspects placed in it were routinely held incommunicado (denied phone calls and visitors) while detectives aggressively interrogated them for confessions without formally charging them.

   • a prisoner is being placed/held on the small book