Spring Bed Bottom.

Patent for a new and improved box-spring. This design consists in "[a] main frame having slats and springs and a metallic frame encircling said springs, in combination with the curved brace-springs having the coils and loops pressing on top of the slats, said springs being secured to the slats and metallic frame, and the rods secured to said frame and passing through the ends of the slats" (lines 76-83)