So I am trying to design and then hopefully build my first wall cabinet for my bathroom due to not being able to find what I want that is prebuilt. It's a simple box with 2 shelves in it 28" x 32" x 12" deep The challenges that I'm thinking about are: the walls that I'm hanging it on are...

I have a scribe with this company's logo "L STRUBLE & CO" on it and have not been able to find any information on the company or tools. The scribe is made of wood with two metal scribes....one being adjustable with a brass thumbscrew. Any help would be greatly appreciated.