re: How to find sewer cleanouts?

I had to call a plumber for this a few years ago. He had an auger with a camera and a light on the end. He sent it down the toilet all the way to where he could see the T joint for the clean out. He had another tool that beeped faster or slower as he held it over the ground. Sort of like a small metal detector but it would pick up the signal of his auger cam. About 4 feet outside the house it went from beeping to solid tone. Sure enough the clean out was a couple feet under right there