Grid alignment syntax – Mathematica Stack Exchange

This is a simple question, but I just cannot understand the explanation given in the Grid documentation page for how to set different alignments for different parts of a grid. I have a grid with two rows with four columns each, and I would like the top row to be bottom aligned and the bottom row to be top aligned. Or, in general, I want to specify one alignment per row (again, for a two row grid). How do I do this?