Transform your old boxes and bags by adding sturdy wire handles. Use 2-3 mm...

https://wiki-velo.win/index.php/How_Much_Extra_Wire_Do_I_Need_for_Anchoring_Tails_on_Each_End%3F

Transform your old boxes and bags by adding sturdy wire handles. Use 2-3 mm galvanized wire for strength and drill 3-3.5 mm holes to fit the wire perfectly