Step 5 · Label Wires

Using small adhesive labels or pieces of tape, clearly mark each wire with the letter of the terminal it was connected to (e.g., 'R', 'G', 'Y', 'W', 'C'). If your old thermostat had a jumper wire (often connecting R and Rc, or R and Rh), note this configuration as well, though many smart thermostats do not require jumpers.