This is half a joke item, and half useful.
Its just a simple mesh square made to look like a prim.
Two of them, one set to 'prim physics' and the other to 'convex hull' physics.
That said, I personally use this as a box around my skybox home - texture it with any image or texture desired, and size it up. Make it solid - and you've got a bit of a box to denote the boundaries of some private space.
I usually make this the same size as my security orb's scan range - peolpe can bounce into it when flying by and be safe, the orb will only hassle people who intentionally teleport inside - and I don't need banlines (which tend to destroy vehicles people are trying to ride).
It's invisible if you're inside it, and you could make it transparent to be invisible on the outside if desired: I use it on a skybox at 4080m up, so I put images on it to let people know that's the edge of my 'spot' but at a height that's not likely to mess with someone's view.
Known flaw: It only has one face - the image you set will be applied 6 times, once per side. I've only dabbled with Blender a little and I couldn't figure out getting different images on each side. So this is free, and very basic. I use it because it had good LOD across distances.
- skybox bounding box
