Give your reclaimed boxes and bags a sturdy upgrade with simple wire handles....

https://wiki-neon.win/index.php/2_mm_vs_3_mm_Wire_for_DIY_Handles:_Which_One_Bends_Easier%3F

Give your reclaimed boxes and bags a sturdy upgrade with simple wire handles. Use 2-3 mm galvanized wire—strong enough to hold heavy items but easy to bend. Drill 3-3.5 mm holes to thread the wire through and twist to secure