That is in the same category as the Saw-Horse, used in RL by the torturers of the Latin American dictators, and described in precise detail by Robbe-Grillet in 'Project pour une revolution dans New York'. The effect of the saw teeth piercing that sensitive part, drawing blood, the strain on legs held still by 20kg weights, the aggravation of the pain caused by the least movement, and prior tortures still adding to the torment, cause the victim to gradually lose consciousness.And there's this option that's not quite as perrmanent.
View attachment 1461878