The base unit is home to ten spring-loaded connectors that let you easily route signal lines from all of your heating and cooling systems into the Nest:

Rc, Rh, W1, W2/AUX, Y1, Y2, G, O/B, Common “C”, Nest star

Responsible for both the wiring and the mounting of the Nest, this component is fitted with two oblong screw holes and a built-in bubble level to aid in a neat and tidy installation.

A few screws stand between us and the base motherboard—a quick turn of the screwdriver, and we see the green.