Carrier TC-NAC Owner's Manual page 14

OPERATING THE THERMOSTAT
9. With the bottom of the thermostat attached to the bottom
of the wall bracket, bring the thermostat back to the jf_ /_
wall. Line up the latch at the top of the thermostat with
the corresponding lip on the wall bracket.
10. Lightly push the thermostat toward the wall. When the
latch and lip are lined up properly, you will hear the
thermostat snap into place.
11. Close the door.