Structure for fastening metallic plate parts together

A chassis assembly for an electronic apparatus comprising:

• a chassis comprising a first sheet-metal part formed of a bottom plate, two opposing side plates each extending upwardly from the bottom plate and having front and rear edges, and a back plate extending upwardly from the bottom plate between the rear edges of the side plates, a top opening of the chassis being defined between the side plates;
• and
• a cover comprising a second sheet-metal part to be assembled to the first sheet-metal part to cover the top opening of the chassis;
• each of the side plates having an L-shaped hooking section and an assembly guide section formed at an upper edge thereof at the top opening of the chassis, each L-shaped hooking section having an entrance facing the rear edge of the side plate, each assembly guide section being disposed rearwardly of one of the L-shaped hooking sections and dimpling inwardly a portion of the side plate to define a recess having a thickness of the second sheet-metal part;
• the cover comprising a cover plate having opposing side edges, each side edge having a L-shaped hooking claw extending downwardly from the side edge to engage with one of the L-shaped hooking sections and a guide lug extending downwardly from the side edge to engage with one of the assembly guide sections, each L-shaped hooking claw having an entrance facing a front edge of the cover plate, each guide lug being disposed rearwardly of one of the L-shaped hooking claws and being sized to laterally slide within one of the assembly guide sections;
• the back plate having an engaging hole and a tapped hole adjacent an upper edge thereof;
• and
• the cover plate having an engaging claw for hookingly engaging with the engaging hole and a screw passing hole aligned with the tapped hole for screw-fixing the cover to the chassis, when the guide lugs are engaged with the assembly guide sections and the L-shaped hooking claws are engaged with the L-shaped hooking sections.