Studs on the Intel LGA support plate push through mounting holes from behind the motherboard (front-left, photo below) and are then topped with plastic spacers (front-right). Mounting brackets are next (rear), followed by nuts (rear-right).
A cross brace is factory-installed to the top of the NH-U14S base, as are a pair of spring-loaded hold-down nuts. These engage studs on the mounting brackets, and the springs assure appropriate pressure between the cooler base and CPU heat spreader.
Noctua also installs the NH-U14S' fan at the factory, though we removed it to access the front mounting nut in the above photo. It’s now clipped back into place.