All dura duplications meet in the sinus rectus (straight sinus), the so called Sutherland fulcrum

Sutherland fulcrum:

The falx cerebelli attaches to the bottom side of the tentorium and runs along the occipital crest from the internal occipital protuberance to the foramen magnum. There it participates in the formation of a strong fiber ring surrounding the foramen magnum and then continues down into the spinal cord as the spinal dura mater.

All dura duplications meet in the sinus rectus (straight sinus), the so called Sutherland fulcrum.