Upgrade your reclaimed boxes and bags by adding sturdy wire handles. Use 2-3 mm...

https://daisydustmaid.com/what-comfort-radius-fits-average-hands-for-a-wire-handle/

Upgrade your reclaimed boxes and bags by adding sturdy wire handles. Use 2-3 mm galvanized wire for durability and thread it through 3-3.5 mm holes for a snug fit