4. Assembly of the front plastic shell and the main frame, with the specific
steps:
1
. Assemble No.1 plastic shell with No.2 plastic shell with M4 screws.
2
. Combine the No.3 plastic shell with the main frame with the M5 screw.
3
. Complete the first two steps and install the No.4 plastic piece from
top down to the No.1 No. No.3 plastic shell.
