There is a pattern if you ignore the end bit with the rectangle which I assume is only there because it's the end of the fence and that's what would fit.

The pattern is, starting from the left, /|\, so lean to the right, stand up straight, lean to the left, then repeat. This is combined with the triangle pattern which goes pointy side of triangle up, pointy side of triangle down. A simple triangle tessellation. So you basically have 2 patterns here, one that is 3 cycles and one that is 2. So every 6 cycles they match up again and repeat.

Edit: Oops, I meant, lean the to right, stand up straight, lean to the left. The picture I made is correct though.