Fences can be amended, lowered, raised, ripped out, strengthened, heightened - they are man-made so man can adjust.
Gates can have locks, secure ones, simple ones, complicated ones or none at all. They can leave out or let in - at the discretion of the one who built them.
But there is also human force that tries to jump the fence, build holes to creep in, break the locks, destroy the gates.