An apparatus includes a computer chassis and a motherboard. The motherboard defines a mounting aperture and a securing hole. The mounting aperture includes a large hole and a small hole communicating with the large hole. The computer chassis includes a bottom plate which defines a screw hole therein. A first convex projection is formed on the bottom plate. A hollow pillar is formed on the first convex projection. The pillar defines a through hole extending through the pillar and the first convex projection. A blind rivet is mounted in the through hole. The blind rivet includes a cap located above the pillar. The cap has an area larger than the small hole. The motherboard is slidable between a first position and a second position. In the first position the motherboard is located on the first convex projection, the pillar extends in the large hole of the motherboard and the cap is positioned above the motherboard. In the second position the pillar is located in the small hole, the cap is misaligned with the large hole, the securing hole of the motherboard is aligned with the screw hole of the bottom plate.