This project documents and transforms into sculpture the peculiar architectural features of the former Namyeong-dong Interrogation Center, a building designed for control and concealment.

Back Door (1:250) converts the floor plans of the building's first and fifth floors into a scale of 1:250—reducing them to the scale of industrial components. The bolt, produced as an axis connecting the two plans, reveals the character of the spiral staircase that directly links the first and fifth floors. Its sixty-eight steps are translated into screw threads, becoming a non-standard component altered from an off-the-shelf industrial product.