As someone who has a 1930's house... the walls are probably plaster and wood lathe. Stud finders don't work very well if at all (https://www.familyhandyman.com/

As someone who has a 1930's house... the walls are probably plaster and wood lathe. Stud finders don't work very well if at all (https://www.familyhandyman.com/article/simple-hack-to-locate-studs-in-plaster-walls/ https://www.familyhandyman.com/article/simple-hack-to-locate...) and cutting into the wall is like chiseling morter... because that basically what you are doing. I love my plaster walls but dealing with pipes/electrcial is a huge pain. I ended up teaching myself to do a passable job with repairing plaster and being content with how it is.