It’s a handling request and often a description of the mailer. “Do Not Bend” envelopes are typically rigid or stay-flat mailers made from stiff paperboard (chipboard) to help minimize creases during transit. They’re commonly used for photos, certificates, prints, and important documents.

• Purpose: Encourage flat handling and reduce bending risk.
• Construction: Sturdy paperboard, often windowless, with self-seal or peel-and-seal flaps and tear strips.
• Common sizes: 6×9, 7×9, 9×12, 9.75×12.25, 12.75×15, 13×18.

The wording alerts handlers, but it isn’t a guarantee. Choosing a rigid mailer with appropriate thickness (often around .020–.028 board) and correct sizing, plus careful packing, can further protect contents.

You’ll see a few names used interchangeably, and they often refer to similar protective designs.

• Rigid mailers or stay-flat mailers: Stiff paperboard envelopes that resist bending.
• No-bend catalog mailers: Catalog-style, open-end envelopes designed to keep contents flat.
• Paperboard/chipboard mailers: Describes the material (board thickness may be noted, e.g., .020 or .028).
• Features to look for: Pressure-sensitive self-seal flaps, tear strips, center seam, windowless faces, and sometimes expansion gussets.

When browsing, search terms like “rigid mailers,” “stay-flat mailers,” or “no bend catalog mailers” can help you locate the right style for photos, documents, or prints.

Pick a mailer with a bit of clearance so edges don’t catch, but not so large that items shift inside.

• 4×6 photos: Typically 6×8.
• 5×7 prints: Typically 7×9.
• 8.5×11 documents: 9×12 or about 9.75×12.25.
• 11×14 prints: Around 12.75×15.
• Large flats (e.g., 13×18): Use 13×18 stay-flat mailers.

Allow roughly 0.25–0.5 inch extra room. For small stacks, consider expansion mailers and thicker board for stiffness. Avoid overfilling so the flap seals flat. Weigh your mail piece and check your carrier’s size guidelines to help determine postage and compatibility.

A few simple steps can improve protection without adding bulk.

1. Sleeve: Place photos or certificates in a clear sleeve to protect against scuffs.
2. Backer: If needed, add a thin backing board for extra rigidity.
3. Right-size mailer: Use a rigid, stay-flat mailer with slight clearance.
4. Stability: Fill minor gaps with a flat insert rather than bulky padding.
5. Seal: Close fully using the peel-and-seal or pressure-sensitive flap; reinforce if necessary.
6. Marking: Write “Do Not Bend” on both sides, away from addresses/barcodes.

These steps can reduce bending risk, but handling conditions vary. For very delicate items, consider extra board protection or a box designed for flat media.

You can shop them online or in the Office Supplies aisle, depending on location.

• Online: Browse Office Supplies > Mailing Supplies > Mailers or Shipping Envelopes. Search for “rigid mailers,” “stay-flat,” or “no bend catalog mailers,” then filter by size (6×9, 9×12, 13×18), color, closure type (self-seal/peel-and-seal), board thickness, recycled content, and pack count.
• In store: Look near envelopes and shipping mailers; availability may vary by store.
• Fulfillment: Delivery or pickup options may be available in your area.

Checking both the outer and usable interior dimensions can help you match your photos or documents accurately.