This 6 bar mechanism enables the hinge to rotate 180 degrees.
It contains 5 movable links, 5 revolution joints and 2 prismatic joints.
The two yellow bodies of the hinge are placed in the holes of the panels and are fixed with screws.
At close position the hinge is not seen from outside.
This hinge is commercially available.
A video shows trajectories of various points of this concealed hinge.
   • 180 deg. concealed hinge 3  

STEP files of this video:
https://www.mediafire.com/file/ecr24y...
Inventor files of this video:
https://www.mediafire.com/file/jojds7...