Exactly what I needed to lift a sunken sidewalk up.Couple tips:1. The dimensions are flexible. 9x17 is only 1 possible configuration, the now you pull in 1 direction the less you will have in the other. So you really need to consider how many "grids" you need. I'm not even sure how you would estimate, but I thought I could use 2, ended up needing just over that.2. Fill with gravel SLOWLY. If you just dunno the rocks on with a wheelbarrow, they will get under the grid and lift it up. It's very difficult to get out back down without removing the rocks.