in the answer provided by @arthurshi , I want to add three points: In the picture, 4 notches were already highlighted with blue circles, but these 4 do not get locked. There are 3 more notches, in green, which gets locked when mouse is closed. 1) There is a hole provided to insert a pin/screw driver, in green down arrow, & gently press the lever to the left, 1st yellow direction. With this the lower portion of mouse will get detached. 2) then, we have to genlty slide the lower case to forward, 2nd yellow direction. For some reason this direction was wrongly mentioned in original answer. 3) Reverse process should be followed to lock the top two notches while assembling the mouse.