Abstract: A security box or a container assembly designed to be secured to the undersurface of a table, counter, bed frame, or like structure so as to extend beneath the undersurface in a substantially out-of-sight location and specifically adapted to hold a handgun or other applicable weapon, valuables or medication in a readily accessible location for easy removal once a cover of the container is opened. To mount the container under a bed, a mounting structure is removably attached to the bed frame so as to support the container in the preferred out-of-sight location beneath the bed in a somewhat cantilevered fashion. Mounting to other surfaces, such as under a table or counter top can be achieved by securing the top of the container to the mounting surface in such a manner as to be out of the general line of sight.