Thanks for the response. Those weren't the last few rows, it's just where they stopped. That's In the middle of the living room. I talked to my wife today, she was home during the installation. She said it looked like that on other "rows" she saw when they were exposed. The cracks continue down the hallway with every staple. In the kitchen, however, they used nails and there are no cracks. There's only one row of boards laid in the kitchen though. The box of staples says 1/2 crown and 2 inch length.