As the title suggests I had to mark the post holes while the existing barn was still standing so I didn't use the old diagonal method. I set it up after sundown and at my first post hole location. I put an axle down the long length of the barn where I wanted it, measuring 60 feet and putting a stake and another stake on the short side at 36 feet. I went to the long axis pole and set up the tripod where the laser crossed that pole, then I put in the last pole and as I moved over there and leveled the laser it separated both poles I had set up on my first setup. . It wouldn't work well during the day, that's the only negative I can suggest.