I have a house built in the 1930s with lath and plaster walls. I was planning to install a hook, so I needed to find a stud. My normal stud finder didn't work (as expected), so I used some rare earth magnets. However, I found that there is about 3-4 inches of something metal all along the top of the wall. This seems to extend to every wall on the floor. I am fairly new to this era house - what could be along the top of all the walls that would be made of metal?
It is likely to be "drywall bead " used to make joins between plasterboard at internal an external corners. It makes it easier for builders or renovators to produce a clean sharp corner.