Why a fence?

People put up a fence for a number of reasons. The two most common are to keep in and to keep out. We have a fence in our backyard for privacy as well as to "keep out". We have a swimming pool and it is required by law that you have a fence so that no one accidentally wonders into your backyard and falls into your pool. When I lived on a farm we had fences to keep the animals in and when we lived in the Philippines we had a fence to keep intruders out.
So what was the purpose of the fence around the Tabernacle?
It was a barrier that prevented unlawful approach.
It was a protection, keeping out all wild beasts.
It was a clear line of demarcation between the world and the holy presence of God.
With a single gate it was the only way of approach to God.
The fence was also tall enough so that anyone could not see over it. It was to remind people that God was holy.