Rōmon 牢問
The Edo-period name for three interrogation methods used to force a confession (flogging, stone-holding and the shrimp tie), as distinct from hanging, the only method then formally called torture.
Rōmon, also read rōdoi, is the collective name for three Edo-period methods of interrogating suspects: flogging, stone-holding and ebi-zeme, in which the body was bound and bent forward like a shrimp. The dictionaries on Kotobank explain that only a fourth method, hanging (tsurushi-zeme), was formally called gōmon (torture) at the time.
Japanese Wikipedia links the system to the 1742 Kujikata Osadamegaki code and to courts that generally needed a confession before a capital conviction. The rōmon methods were applied in rising order in the prison, and hanging followed only if the suspect still refused. Both sources say flogging and stone-holding were common, while the shrimp tie was rarely used. Japan formally abolished torture in 1879. See also ebi.