If you’re opposed to using a stud finder because you think that they don’t work, it’s probably because you’re using it wrong.
Stud finders are available in configurations as basic and inexpensive as a magnet or as complex and pricey as a wall scanner and everywhere in between. It seems a lot of people find them either unreliable or inaccurate, though – especially the more popular mid-range models that beep and light up. I have a mid-range model that sits in my tool box and, to be honest, I can’t remember the last time that I used it. Most of the time I use the knocking method, or the magnet on my Razorscribe, or I look for poorly filled nail holes in the baseboard as a guide. But after watching Ron Paulk’s video below, I am going to give my intermediate wall scanner another try. His tips are simple and straight forward, but worth a look – especially if you have one of these that you’re not using. Even if you do, Paulk’s advice might give you more accurate results. Calibration is key, as is understanding the limits of the particular model that you're using.