Buying expensive stud finders is probably the easiest route for most handyman, but the cost is high.
There is a simpler and cheaper way to find the door post inside the wall, but you need patience.
This handy video tutorial will show you how to find bolts with magnets in inlaid wall partitions.
But what if your bolts are not aluminum or steel?
It doesn't matter, the magnet searches the metal screws in the wood nails.
You find a place to stick together and then up or down in the vertical direction to see if there is another screw.
If that's the case, it's a horse.