Prison

What better place for restraints than a prison. Plenty of opportunities to find people locked away with no chance of escape.

Did someone commit a great offence and needs to be bound head to toe in order to make sure they don't escape? An sentence for some trivial crime? Or maybe they were targeted to be arrested even though they're innocent and don't deserve punishment at all?

Perhaps you aren't even a prisoner but are instead a sadistic guard who revels in torturing the inmates or the warden in charge of deciding what restraints and punishments are needed.

Maybe the jail itself is abnormal, it's real purpose rehabilitating inmates into sex slaves, mind controlling men into sissy maids, punishing them until they become masochistic gimps or keeping them in pods to be endlessly tickled.