Apparatus, mounting structure, and mounting method

A mounting structure of mounting a plurality of printed board units to a housing, wherein

• each of the plurality of printed board units includes
• a printed board that has heat generating parts arranged thereon,
• a frame that has the printed board arranged therein,
• a first rail arranged at a first lower end of the frame having the printed board located thereon, and
• a second rail arranged at a second lower end opposed to the first lower end in an opening, and wherein
• the housing includes
• a rail holding unit that movably holds the first rail of a first printed board unit and the second rail of a second printed board unit adjacent to the first printed board unit, the first printed board unit and the second printed board unit being included in the plurality of printed board units, the rail holding unit being formed by including upright wall portions and a rail receiver, the upright wall portions, between which the rail receiver is located, being erected at sides of the rail receiver, the rail receiver receiving the first rail and the second rail, the rail receiver having a cross-sectional shape conforming to a square U-shape which opens downwardly, the cross-sectional shape being a shape of a cross-section for a movable direction of the first rail and the second rail, and
• a cooling fan arranged on an upper side or an underside of the housing to send air into the frame,
• wherein each of the first rail and the second rail is disposed on an extension of a side wall portion of the frame, and
• a width of the rail receiver in the rail holding unit is set larger than a total of a width of the first rail and a width of the second rail.