What Is a Slotted Box? Cardboard Box Styles Explained for Packers

A slotted box is the plain cardboard carton most of us picture when we think of a box: a tube of corrugated board with four flaps at the top and four at the bottom. You fold it up from flat, fold the flaps in and tape them shut. It is the most common style for shipping, storage and moving.

Other styles do some jobs better, such as crash lock boxes for speed and die cut boxes for small items. Pack Solution stocks standard flap cartons, crash lock, die cut and PIP boxes. We do not make custom printed, half slotted, full overlap or telescope boxes.

Quick Picks: Slotted Box and Other Box Styles

These three cover most packing jobs, from small postal orders to heavy cartons.

Best for everyday orders in a standard flap carton

Single Wall Cardboard Boxes

Light corrugated boxes in standard sizes, supplied flat, for e-commerce orders, storage and light moving.

• 15 sizes, 5 x 5 x 5" to 24 x 18 x 18"
• Includes a 450 x 350 x 160mm Small Parcel Max box
• Minimum 5 per size

From £0.35 ex VAT (£0.42 inc VAT)

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Best for fast packing with no tape on the base

Crash Lock Boxes

Cardboard boxes with an automatic base that locks into place as you open the box.

• 10 sizes, CL-A (100 x 100 x 70mm) to CL-K (426 x 300 x 300mm)
• No tape needed underneath
• Minimum 5 per size

From £0.59 ex VAT (£0.71 inc VAT)

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Best for small orders that fold up without tape

Die Cut Boxes Brown 070502

Fold-together brown postal boxes cut to shape, which lock together as you fold them.

• Pack of 50
• Supplied flat
• No tape needed to assemble

£20.00 ex VAT (£24.00 inc VAT)

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• Single Wall Cardboard Boxes are standard flap cartons in 15 sizes, from 5 x 5 x 5" to 24 x 18 x 18".
• Double Wall Cardboard Boxes come in 12 sizes, from 9 x 6 x 6" to 24 x 24 x 24".
• Crash Lock Boxes come in 10 sizes, CL-A (100 x 100 x 70mm) to CL-K (426 x 300 x 300mm).
• Die Cut Boxes Brown 070502 fold together without tape, in packs of 50.
• PIP Large Letter boxes are die cut and 20mm deep.
• Brown Packing Tape comes in packs of 6 rolls, 48mm or 72mm wide.

What Is a Slotted Box?

A slotted box is a carton cut from a single sheet of corrugated board, with slots between the flaps so they fold. One side seam, glued, stitched or taped at the factory, turns the sheet into a tube.

The flaps at each end close the box. Two flaps run along the long sides, and these are the outer flaps. The two on the short sides are the inner flaps, and they fold in first. Close the outer flaps over them, tape the seam and the box is sealed.

The design wastes very little board, which is why it is the default carton across the packaging trade. It also packs flat, so a stack of hundreds takes up little room until you need them. The standard flap cartons we sell, in both Single Wall Cardboard Boxes and Double Wall Cardboard Boxes, are built this way.

How a Regular Slotted Box Is Built

In a regular slotted container, or RSC, all four flaps at each end are the same length, and each measures half the width of the box. The two outer flaps therefore meet exactly in the middle when closed.

The inner flaps are the same length, but because the box is longer than it is wide, they usually leave a gap between them. That gap is normal. On a square box such as 12 x 12 x 12", the inner flaps meet in the middle too.

Box sizes for slotted cartons are given as length x width x height. Our single wall sizes are listed as internal measurements, so the item you pack must fit inside those figures with room for wrapping.

Building a Slotted Box From Flat

A flat slotted box opens into a tube when you push the two folded edges towards each other. Square it up so the corners sit at right angles, then fold the bottom inner flaps in, followed by the outer flaps. Tape the base while the box is still empty and upside down, then turn it over to fill. Fold along the score lines each time; a flap folded beside its crease will not sit flat and leaves a weak edge for the tape to cover.

FEFCO Box Styles in Plain English

FEFCO is the European federation of corrugated board makers, and its code gives each carton style a four-digit number. The regular slotted container is 0201, the code most box makers recognise.

You do not need the codes to buy boxes, but they help when you compare suppliers or read a specification sheet. The fefco box styles below are the ones packers meet most often.

The FEFCO code describes the shape only. A 0201 box can be made in single wall or double wall board, and the board grade is a separate choice.

Slotted Box vs Crash Lock, Die Cut and PIP Boxes

The slotted box is the most flexible style, but other box styles are faster to build or better for small items. The right choice depends on size, weight and how many orders you pack each day.

Crash Lock Boxes have a base that folds and locks by itself as you open the box, so only the top needs closing. That saves time and tape on a busy bench. Die Cut Boxes Brown 070502 fold together by hand from a flat blank and need no tape to assemble; call or email for the exact internal dimensions before you order.

Royal Mail PIP Large Letter boxes are also die cut, but made only 20mm deep, for slim items posted at the Large Letter rate. Our guide to die cut, crash lock and PIP boxes compares those three in more depth, and the sibling guide to Royal Mail packaging boxes and bags matches box sizes to the postage bands.

Single Wall or Double Wall Board

The style of a box and the board it is made from are two separate choices. A slotted box can be single wall for light orders or double wall for heavy ones.

Single wall board has one layer of fluting between two liners. It is light, which keeps postage weight down, and it suits clothing, books, homeware and most e-commerce orders. The single wall range also includes a 15.35 x 11.6 x 7.3" (390 x 295 x 185mm) box listed as Extra Strong, and a 450 x 350 x 160mm box sized to the Royal Mail Small Parcel maximum.

Best for heavy, fragile or high value goods

Double Wall Cardboard Boxes

Heavy duty corrugated boxes with two layers of fluting, stiffer than single wall and better for stacking.

• 12 sizes, 9 x 6 x 6" to 24 x 24 x 24"
• Two layers of fluting
• Sold per box

From £0.59 ex VAT (£0.71 inc VAT)

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Double wall board has two layers of fluting. It is stiffer, stacks better and protects heavy, fragile or high value goods. Pick double wall for moving house, for anything heavy enough that the base could sag, and for parcels that travel a long way. Our single wall vs double wall guide goes further into the difference.

When you stack slotted boxes, put the heaviest at the bottom and line up the corners. Most of a carton's strength sits in its four vertical edges, so a box resting across the gap between two boxes below it will crush more easily. Fill each box so the top flaps close flat. An underfilled box caves in when another is stacked on it, and an overfilled one bulges and splits along the seam.

How to Tape a Slotted Box With an H Seal

An H seal uses three strips of tape on each end: one along the centre seam and one across each end edge. Seen from above, the tape forms a letter H.

1. Fold the inner flaps in, then the outer flaps over them.
2. Run tape along the centre seam, letting it run down each end of the box by a few centimetres.
3. Run a strip across one end edge, covering the ends of the flaps.
4. Run a strip across the other end edge.
5. Turn the box over and repeat on the base before you fill it.
6. Press every strip down firmly so the adhesive grips the board.

Brown Packing Tape matches brown cartons. The standard 48mm x 66m roll suits most boxes, the 132m and 150m rolls need changing less often, and the Proloc 72mm x 66m roll covers more of the seam on heavy cartons. The BigTape and Vibac 835 Buff rolls unwind more quietly, which helps in shared packing areas.

Best for sealing slotted boxes

Brown Packing Tape

Buff polypropylene tape that matches brown cartons, in five rolls from 48mm x 66m to 72mm wide.

• 48mm x 66m standard roll, 42 micron
• Proloc 72mm x 66m for heavy cartons
• Packs of 6 rolls

From £4.50 ex VAT (£5.40 inc VAT)

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Which Box Style for Which Job

Match the style to the product and the pace of your packing. Slotted boxes cover the widest range of sizes, while the other styles save time on small, repeat orders.

• Mixed orders in many sizes: single wall slotted boxes, since there is a size for most items.
• Heavy goods and house moves: double wall slotted boxes.
• The same small product many times a day: crash lock boxes, which build in seconds.
• Small gifts and accessories: die cut boxes that fold up without tape.
• Slim, flat items: PIP Large Letter boxes, 20mm deep.

Size comes next. Our sibling cardboard box sizes chart lists every size we stock in inches, millimetres and centimetres, so you can match a box to your item once you have chosen the style.

Slotted Box Checklist

• Choose the style first, then the board, then the size.
• Fold inner flaps in before outer flaps.
• Tape the base before you fill the box.
• Use an H seal on heavy boxes, top and bottom.
• Use 72mm tape for large or heavy cartons.
• Pick crash lock or die cut boxes for fast, small orders.
• Keep labels away from the side seam and tape.

Stocking the Right Box Styles

Most packing benches need a few sizes of slotted box for everyday orders, plus one quicker style for small, repeat products. Add a roll or two of brown tape and you can pack nearly anything you sell. The boxes and tapes collections hold every style and roll covered here, and they are a quick way to compare the cardboard box types side by side.

Frequently Asked Questions

What is a slotted box?

A slotted box is a cardboard carton made from one piece of corrugated board, joined at one side seam, with four flaps at the top and four at the bottom. The slots cut between the flaps let them fold. In the regular style all flaps are the same length and the two outer flaps meet in the middle.

What does RSC mean on a cardboard box?

RSC stands for regular slotted container. It is the most common carton style, listed as 0201 in the FEFCO code used in Europe. The outer flaps each measure half the box width, so they meet at the centre when closed. It ships flat and needs tape top and bottom.

What are the main cardboard box types for posting?

For most sellers the main styles are the standard slotted carton, the crash lock box with an automatic base, the die cut fold-together box and the slim PIP Large Letter box. Our Crash Lock Boxes run from CL-A (100 x 100 x 70mm) to CL-K (426 x 300 x 300mm).

Are your single wall and double wall boxes slotted boxes?

They are standard flap cartons, the style the packaging trade calls a regular slotted container. They arrive flat, and you fold them and tape the flaps. Single Wall Cardboard Boxes come in 15 sizes and Double Wall Cardboard Boxes in 12 sizes, from 9 x 6 x 6 inches to 24 x 24 x 24 inches.

How do I tape a slotted box?

Use an H seal. Run one strip of tape along the centre seam where the outer flaps meet, letting it overlap down each end by a few centimetres. Then run a strip across each end edge. Do the same on the base. For heavy boxes, use a wider tape such as 72mm.

Do you sell custom printed or half slotted boxes?

No. We stock standard flap cartons in single and double wall, crash lock boxes, die cut boxes and PIP Large Letter boxes, all in plain brown. We do not make custom printed boxes, half slotted containers, full overlap cartons or telescope boxes.

Shop for This Job

• Cardboard Boxes
• Packing Tapes

Related Guides

• Cardboard Box Sizes Chart: Dimensions in Inches, mm and cm
• Royal Mail Packaging: Boxes and Bags That Fit Royal Mail Size Bands
• Single Wall vs Double Wall Boxes: Which to Choose
• Letter Box Boxes Die Cut Crash Lock Pip

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