The basic structure and photos have already been explained on this site and on Wikipedia:
Variable-sweep wing, Wikipedia
Looking at it, I understood that the pin and pivot that make up the axis of rotation and the link bar provided in front of that axis form the basic mechanical structure.
However, it is not clear why the structure produces traces of contact only in front of the axis on the undersurface skin of the wing.
Modified from an answer here
My guess is that it is equipped with a guide contact. However, such a policy stresses thin skins. I also speculate that the skin is not an accurate plane. That seems absurd.
I also considered the deformation of the pylon as a candidate, but from the viewpoint of the aerodynamics of the payload, I thought that the upward aerodynamics would not be applied to the front because it moves downward from the head when falling.
Please tell me why the structure has an arc mark in front.