cut away the drywall between two vertical studs, and insert a horizontal stud between the two, to attach the rail to.

You could try Molly/toggle bolts? But I don't know how much the med cab and its contents will weigh.

Studs are every 16''. Tapping a wall isn't a substitute for a stud finder. You will be able to find a stud with the proper tools. Check for wall flatness with a level as well. You want the cabinet to snug up to the wall, and sometimes a drywall seam hump will pevent that.

Thanks lwo. I am waiting for my carpenter to do the installation and he will have a stud finder so we will know at that time whether he needs to beef up the wall. But I have a recollection from when the vanity was installed that it was not screwed in under the sink because of the lack of a stud. The dreaded drywall seam hump is why I would like to avoid have to do drywall work on that wall - you are right that it will affect how the cabinet sits against the wall.

This isn't a microwave oven. Toggle it and forget it.

haha! That's exactly what my DH said.

I just hung one today with no studs! We just used mollies. So far so good it's still up and seems sturdy. I'll let you know if it crashes down during the night ðÂÂÂ