Secure String & Button Closure for Reliable Storage: Classic string and button closure keeps your file storage boxes with lids securely closed—ideal for document storage, moving, and long-term archiving. Heavy-Duty Strength You Can Stack On: Built with a 750lb stacking strength, these corrugate file boxes with locking lids are the go-to solution for secure, stackable document storage - ideal for long-term archiving in busy offices. FastFold Assembly Saves Time: These file storage boxes with lids pop open in seconds - no tape, no hassle. Perfect for professionals who value quick setup during audits, moves, or quarterly cleanups. Easy to Carry with Built-In Reinforced Handles: Move your storage file boxes confidently with tear-resistant hand holes - designed for easy lifting and carrying between offices, rooms, or locations. Sized for Letter Files: Each file storage box is perfectly sized to hold standard letter-size files and folders - making it easy to organize everyday paperwork, invoices, and office documents. Collapsible & Reusable Design: When not in use, these file storage boxes fold flat for compact storage. Reuse them again and again - ideal for seasonal records, rotating client files, temporary storage needs, or seasonal storage.