In your face. Literally.

The skull is an amazing piece of construction. There are ridiculously many small pieces it consists of. The outline is pretty much a few larger bones, but the face, oh the face, the face is like a jigsaw puzzle. Lots of pieces that barely fit together, mostly by leaving huge gaps between one another.
For instance, take the eye hole, the small place where one of your eyeballs is located. A half-sphere hole that is made up of 7 bones. The nasal cavity has even more bones, but that’s because it is called one hole even though it has a bone wall smack in the middle of it, dividing it into two, but it is still called one nevertheless. Pretty much all of the bones are connected to a single bone right in the middle of the skull. This bone is somewhat peculiar – it has two sets of wings.
To make matters worse, there is a set of tiny holes and a horn of sorts right inside the forehead. One of those holes may or may not be a hole. It may or may not contain a vein. That vein that may or may not be there also may or may not reach the nasal cavity and drain it. That may or may not be a problem as the nasal cavity can contain all sorts of bad stuff you don’t want heading towards your brain^[1]. It’s not an exact science.