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

https://sierra-wiki.win/index.php/How_Do_I_Reinforce_Cardboard_Before_Drilling_Holes_for_Handles%3F

Upgrade your reclaimed boxes and bags by adding sturdy wire handles. Using 2-3 mm galvanized wire, you can create strong, rust-resistant grips that last. Drill 3-3.5 mm holes to thread the wire through easily