If you export a part from roblox, and open it in blender, it has an edge down the middle of it, usually diagonally.

Why is this, and when modelling my own stuff, should I also do this?
If you export a part from roblox, and open it in blender, it has an edge down the middle of it, usually diagonally.

Why is this, and when modelling my own stuff, should I also do this?
All models are comprised of triangles to form a shape. This is what you’re seeing here.
Blender abstracts this away for you when dealing with quads, but under the hood this is still how your models are being represented.
It is recommended you stick to quads when modelling.