From that first rush to surround the soon-to-be-broken- down APC, we find a fraternization performance that amounts to a ritualized trespassing.
In Egypt, military space is usually strictly guarded and "separated" from the public. By climbing onto tanks (trespassing), protestors symbolically broke the army's "right of separateness" and forced the soldiers into personal, face to face interactions that made it harder for them to fire on the crowd.