How would you make an out of bounds for a map?
There any any one of thousands of ways, but until you give more detail, you’ll know of none of them.
What exactly do you want to accomplish?
Yeah, it’s really so simple that there are thousands of ways to do it.
The problem is, we have no idea what you are doing.
What can’t go out of bounds? Where are the bounds? Is it in a 2d plan, a 3d volume? etc…
My recommendation is to learn more about game programming and you will easily know how to figure it out yourself.
For instance, if you just want to prevent a FPS player from walking outside a certain area, check their coordinates and prevent them from going outside, or give a warning, or whatever you want to do that you haven’t told us yet. That’s less than an hour of coding.
Or just build invisible walls, if you don’t want any warning messages or anything special.
But first, go read up on how to make games in general, learn a programming language, then come back to Unity?