Stud Finder.
Knocking can get it done, but the surety of knowing is a nice to have for sure.
I've got a basic Zircon one, but my handyman has this fancier one: https://www.homedepot.com/p/Franklin-Sensors-ProSensor-M210-Center-and-Edge-Professional-Stud-Finder-FSM21012HD/317740851 Thinking of getting something like that.
For a cheap option, you can also use a magnet that's strong enough to find the drywall screws (assuming the construction is a wood frame with drywall)
Project Farm did a comparison video thay may be handy when you're in the market for a new stud finder
Here is an alternative Piped link(s): https://piped.video/sWMJhfMPWn4
Piped is a privacy-respecting open-source alternative frontend to YouTube.
I'm open-source, check me out at GitHub.
Add a string and a small weight, and you've got a good plumb-bob to make the vertical stud more evident.
Bonus functionality: running it over your chest and making beeping noises to make your wife scowl at you
I've bought multiple digital stud finders, not sure if they were bad but didn't even work half the time. Ended up buying a strong magnet and works way better since it finds the screws that hold the drywall up
Do you have one you recommend? I bought one but either I'm not using it correctly(most likely) or it doesn't work consistently.
I have a Bosch one from their professional range. Finds not only studs, but also wires, etc. Super useful, but expensive.