To be situated between a mattress and a box spring is a hinged frame that includes inflatable bags located respectively beneath the head and foot portions of the mattress. A controlled pump unit permits selective inflating of the bags so as individually to elevate the different portions of the mattress at the command of a user. Construction features of one version include internal contour-defining elements tied between space-opposed supports affixed to the walls of the bags and double-plate supports readily mounted into the bags and which enable tying of the bags to the frame. Another version uses an arrangement of straps to define contour.