Generally speaking, a conventional case assembly for electronic appliance relies on the connection of multiple bolts which decide the quality of the case assembly. For instance, the reliability of the case assembly depends on the connection of the bolts and the cases, however, the bolts have to be threadedly connected to the cases one by one and which is a time-consuming task. The threaded holes can be easily broken and affect the connection of the bolts which may drop from the cases. U.S. Pat. No. 7,092,520 to Fuhrmann discloses the invention related to the connection of the bolts and the cases.