Watch out for sensory issues. If the kid reacts to, I dunno, styrofoam like it's full of shards of broken glass and he can't bear to touch it, keep him away from styrofoam

Central case of torture: thumb screws or the rack

Obviously within spitting distance of the central case: Forcing someone to press their hand down on broken glass

Still pretty obviously in the neighborhood: Forcing someone who reacts to styrofoam like it's broken glass to touch styrofoam.

You're mixing up the cases.