We have a 5' x 3' flower garden under our mailbox along the road and we're trying edge it with concrete pavers on end. We have the back row complete. We used 2 stakes with a string and a torpedo level to be sure the bricks were level and the same height.

Now the problem: we added the pavers on the short sides, which are level with the back row paver on each end. But one short side appears to be higher than the other. How can this be? Any help is greatly appreciated!

Thank you!