I now have a different interpretation of what you're saying. They do have opposing angles. When you sew the rows together, you have to turn the row in the other direction for the angles to meet evenly. If you have a tumbler with a smaller angle as your first tumbler and the row that you want to put next to it has the wider angle, you need to turn that row basically upside down to get the two wider angles to meet, and then every tumbler going down will meet its appropriately wide tumbler.