The International Baccalaureate formats the space for candidate responses with “dotted lines in box”.  I was mildly peeved since the change that I couldn’t typeset questions with the exact same format.  Here is a style file for use with the exam class that sets “IB formatted” questions.  This style file sits in the same directory as your .tex and requires the tcolorbox package.  Your preamble would look something like:

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\documentclass[a4paper, addpoints]{exam}
\usepackage{tcolorbox}
\usepackage{solutionorib
}

The solutions are to be wrapped in a solutionorIB environment:

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\begin{solutionorIB}[0.6in]
  % solution goes here
\end{solutionorIB}

The output:

solutionorIB environment for the exam class

solutionorIB environment for the exam class

I am not yet familiar enough with the tcolorbox package to drop the top down so it can be fully symmetric.