Inner Lining

Hello All.

I am currently having an issue where I am trying to create an object then simply fill on the inside of the line, see image.

I am currently working around creating object, making it slightly smaller then placing on the inside of the original object. Ideally, there would be a button that says "fill inside line by XXX mm." or something to that effect.

I wonder if anyone has a workaround? 

Thanks in advance.

Kind regards