Honeywell RTH7500 Guide D'installation page 16

Installation Guide
Remove tab and mount thermostat About your new thermostat
Remove tab.
Align pins on back of thermostat with
slots in wallplate, then push gently until
thermostat snaps into place.
TIP: If wires interfere when you try to mount the
thermostat, push excess wire back into the wall opening.
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