Lenovo C225 All-In-One - Manual (Page 54)

For models C220 refer to the below illustration. (7 screws)
For models C225 and C325 refer to the below illustration. (7 screws)
For models C320 refer to the below illustration. (9 screws)
Step 17. Place the new motherboard into the chassis, aligning the screw holes in the motherboard with
the mounting holes in the chassis.
Step 18. Secure the new motherboard to the chassis using the screws.
Step 19. Attach all related components to the new motherboard.
50 Lenovo C2/C3 Hardware Maintenance Manual