This free sewing pattern offers a basic, customizable design for boys’ underwear, suitable for ages 18 months to 6 years. The pattern allows adjustments for leg openings and waistline to ensure a better fit, and can even be adapted to create swim trunks. It’s available for free and comes with a non-commercial license. The pattern is easy to use, with sizing based on measurements provided in the size chart. For more details, visit Szyciebielizny.