Boxes

• How to Avoid Underfull \hbox Warnings with Subfigures
  Underfull \hbox warnings are not caused by subfigures automatically. Check the log, fit the subfigure widths, and fix the paragraph or box that is too loose.
• How to Change Line Spacing in a Shortstack-Like Box
  Use a one-column tabular box instead of \shortstack, then adjust its row spacing with a local \arraystretch value or a row-specific gap.
• How to Add a Border or Frame Around a Box in LaTeX
  Use \fbox for a simple LaTeX border, or frame a minipage for paragraphs; control padding and line thickness with \fboxsep and \fboxrule.