HTC One M9(s) facing up, the
nano SIM slot is on the left side and the
microSD slot on the right side.
There are trays inside the slots that are used for inserting your cards.
When inserting the eject tool into the tray eject holes to remove the card trays, make sure not to press on the trays to avoid damaging the eject mechanism inside the slots.
Also, if you want to use a protective case, make sure to buy a case that's designed for
HTC One M9(s) and that doesn't block the trays.