Makeshift Fence is indestructible!!!

Hello,
I built a Makeshift Fence and realized he had made a mistake, but I can not break it. I have 10/10/10/10 and Wooden Shovel.
Why?
What should I do?
I built a Makeshift Fence and realized he had made a mistake, but I can not break it. I have 10/10/10/10 and Wooden Shovel.

What should I do?