Sleep unit having adjustable firmness

A sleep unit, comprising interconnected top, bottom, side and end walls, a plurality of spaced inner coil springs arranged in rows parallel to said side and end walls and extending between said top and bottom walls, said springs having spring turns spaced apart a predetermined distance, a movable spring engagable, flat wall disposed within the unit between said walls thereof, said movable wall having a plurality of spaced portions extending parallel to said rows of springs, said portions each having a thickness less than said predetermined distance, and openings in said movable wall located between said spaced portions, said springs extending through said openings in an out-of-service position of said movable wall, one of said side and end walls having an opening defining guide slots for said movable wall, and said movable wall having a handle extending through said opening in said one wall, said guide slots extending in a direction parallel to said top and bottom walls, and a portion of said handle extending into a selected one of said guide slots upon manually shifting said movable wall from said out-of-service position to an in-service position in a direction perpendicular to said springs for inserting said portions of said movable frame into selected one of said turns of said coil springs for thereby adjusting the firmness of the sleep unit.