Custom Side Loading Mailers for Flat, Slim Items

What are side loading mailers?

They are flat-packed corrugated boxes that fold around your product and close at a short end. The opening sits on the side, not on top.

You get a solid top panel with no lid seam. That panel is easy to label or print.

If your goods are mostly paper, compare them with our slim mailers for paperwork and brochures. A side loader is usually a bit sturdier.

Why load from the side instead of the top?

Flat goods are hard to lower into a top-opening box. Edges catch on the walls, and the lid ends up sitting loose.

A side loader lets the product glide along the base. The walls hug it once the flaps are folded. Many packers like that the box stays flat on the table the whole time.

The build also uses less board. There is no deep lid and no extra wall, so the box stays slim and light.

How do I work out the right inside size?

Measure the length, width and thickness of the item. Add about 1/8 in to the length and width so it slides in without a fight. Add a little height if you wrap the product first.

Height is the number that matters most. Extra room lets the product rattle, and too little makes loading slow. Our guide on measuring the inside of a box shows the method step by step.

If you sell one book and also sets of two, tell us both thicknesses. Two heights often cost less than filling a tall box with paper.

Which board should I choose?

Most side loaders are single wall corrugated in kraft or white. Pick by the weight of the product and how hard its corners are.

E flute is enough for most prints, paperwork and a single light book. Move up to B flute for frames or a stack of titles. Our flute guide for corrugated board explains the differences.

Can side loading mailers be printed?

Yes. The wide top panel suits a logo, a pattern or a short message. We print plain, one color, two color or full color CMYK, outside and inside.

White board gives clean, bright color. Kraft has a warmer look and works well with black or white ink. Matte or gloss lamination, spot UV, foil and embossing are available too.

Many shops keep these boxes plain or one color, since they are mainly for shipping. Place your artwork in Design Your Box, and our designers will help with layout. You see a free proof before anything is printed.

Is a side loader safer than a padded mailer?

A padded mailer is light and cheap, but it bends. A print, a certificate or a hardcover can crease inside one.

A side loading box gives you a rigid shell on every side. Corrugated board resists bending far better than paper padding. The closed ends also guard the corners.

If you also sell soft goods like scarves, a padded paper mailer for soft items is a fair match. Use the side loader for anything stiff.

What mistakes should I avoid?

The biggest one is ordering a box that is too tall. The design works because it grips the product, and spare height undoes that.

Another is skipping tape. The tuck flap holds on a desk, but a bumpy trip can work it loose. Also keep the label off the opening, or your customer must cut through it.

Check your proof as well. No text or logo should cross the tuck fold, where it would split or hide.

How do I order side loading mailers?

Pricing starts from $0.30 a box. The exact figure depends on size, board and print, and we send it in your emailed quote within one business day.

Send your item sizes through our quote request for custom mailers, or write to info@ordercardboardboxes.com. After you approve the proof, production takes 4–6 business days. Free tracked shipping to any US address takes 2–3 business days.