The Heck House was an alternative façade for the First Church of Springfield, which was available during the Treehouse of Horror XXIII Event in late 2012. It returned during the Treehouse of Horror XXIV Event as a premium item. For Devil Flanders to Inspect the Hell Labs you must have the façade on. If you have the façade but not switched to then he can't preform the job.
Simpsons Wiki DescriptionEdit
When Bart, Lisa, Milhouse and Nelson were terrorizing the Town with pranks (although Lisa was hardly involved), Ned Flanders attempted to stop the children's shenanigans by scaring them. He transformed the Church in to a "Heck-House". After failing to scare them, Ned Prayed to God for unholy powers, thus becoming Satan. He showed the kids what sins would send them to Hell, and what happens to Sinners when in hell.