This picture shows my installation of a toilet paper holder. On my bathroom vanity there is an unused space above the lower main cabinet. Opening the cabinet door gives complete access to the area behind the unused space. I just installed four expansion bolts, the kind that "blossom" out on the backside. This is a one-way deal so make sure you line them up exactly to match the holes on the toilet paper holder. I don't know of any "Plan B."