Tuck End Auto Bottom Boxes with a Pre-Glued Crash Lock Base

What are tuck end auto bottom boxes?

They are folding cartons with a lid you tuck and a base you never touch. Most people know them as auto bottom boxes or crash lock boxes. The names describe the same thing.

The base is built from four flaps. Two of them are glued to their neighbours on the gluing line before the carton leaves us. When you squeeze the flat carton open, those glued pairs swing round and hook into each other.

It is one of six closures in our tuck end box styles range, and the one we suggest most often for anything in glass.

How does a crash lock base work?

Look at the middle photo, where the carton is open from above. You can see the base flaps folded in at an angle, each one tucked under the next. They form a floor that does not depend on a tuck tongue.

In the third photo the cartons sit in a group, and one shows its underside. The flaps meet in a pinwheel pattern across the base.

Because the base is glued, it does not spring open when a full carton is picked up by the lid end. That is the main reason people choose it for jars and bottles.

Who uses auto bottom boxes?

Anyone whose product sits on its base and has some heft to it. Candle makers are the classic example, and our printed candle tuck boxes mostly use this closure.

They also suit brands who pack in volume. Not folding the base saves a movement on every carton, and over a few hundred units that adds up.

• Candle studios boxing glass jars and tins
• Honey, jam and sauce makers
• Supplement brands with tubs and pots
• Diffuser and room spray makers
• Gift shops boxing mugs, glasses and small ornaments

Auto bottom or plain tuck base?

Both arrive flat and both use the same board and finishes. The difference is all in the base and in how you pack.

For a light lipstick or a card deck, a tuck base is enough. For a glass jar, the crash lock base is the safer habit.

What size auto bottom box fits a candle jar?

Measure the jar across its widest point, usually the rim or the lid. Then measure the height with the lid on. Add about 2 mm to the width each way and 4 or 5 mm to the height.

Take a common 20 cl candle jar: roughly 82 mm wide, and 90 mm high once the lid is fitted. That gives a carton of about 85 × 85 × 95 mm inside.

Tins and jars with a wooden lid often vary by a few millimetres between batches. Our step-by-step tuck box measuring guide covers clearance in more detail.

Board and print on a crash lock carton

We print auto bottom boxes on 350gsm white SBS as standard. Kraft is popular for candles and food, and other boards can be quoted.

Our first and third photos show natural kraft. One set carries a small, scattered illustration on the side panels. The middle photo shows a white-lined carton with a photo panel printed on the front.

Print the base if you like, but remember the customer rarely sees it. Most brands put ingredients and the barcode on a side panel instead.

Can I add a window or insert to an auto bottom box?

Yes. A die-cut window on the front or side lets a candle colour show through, with or without clear film. Keep it a little way above the base, where the crash lock flaps sit inside.

A card insert can hold a jar in the centre or lift a short product. With a window, the candle boxes with a front window are a good model to follow.

Both are cut on the same die as the carton and shown on the proof.

How quick is packing with a crash lock base?

Very. Pick up a flat carton, press the two folded edges towards each other and the tube opens. As it squares up, the base drops and locks.

Drop the product in from the top, fold the dust flaps and push the tuck home. There is no second end to close.

Keep a few cartons opened ahead of you on the bench and fill them in a batch. Do not open a whole box of them at once; open cartons take up a lot of room.

Common mistakes with auto bottom cartons

We spot most of these on the proof, but they are easier to avoid at the start.

• Very shallow cartons: the base flaps need some depth to lock, so we may suggest another bottom
• Measuring the jar without its lid
• Placing a window low on the front, over the base flaps
• Forcing the base open from inside instead of squaring the tube
• Putting the barcode on the base, where the flaps break it up

How do I order auto bottom boxes?

Every crash lock run is priced in writing from £0.25 per unit, with the figure depending on size, board and quantity. Send whatever you have so far, even if it is only a jar size and a rough quantity. We fill the gaps and come back with questions. You can get a written price for crash lock cartons using the steps below.

1. Measure the jar or bottle with its lid on, or send us one.
2. Choose white SBS or kraft, and any finish or window.
3. Send a logo or print-ready file; our designers set it on the dieline for free.
4. Approve the proof, which shows the base flaps and every panel.
5. Production takes 4–6 business days, and delivery to your door is free, tracked and 2–3 business days.