Is there a a scalable relationship between a part's size and the position of its edge?

I have a script that will take any part named "Floor" and recreate it with 10x10 parts arranged in a grid, but I'm not sure how to get the grid to lay exactly where the "Floor" part was. I need to know the position of the Floor's edge so that I can know where to start placing the 10x10 parts. Does anyone know the relationship between a part's size and the position of its edge or any way to align one part on the very tip of another part's edge?