Look at a flat folding carton blank and you will see a narrow strip along one vertical edge, usually tapered slightly at the top and bottom. That is the glue tab, also called the glue flap or the side seam flap. It is the piece that turns four printed panels into a tube.
What it does
During manufacture the blank passes through a folder gluer. Adhesive is applied to the tab, the blank folds, and the tab bonds to the inside face of the panel at the opposite edge. The carton is then shipped flat as a collapsed tube and squared up at the point of filling. Without the tab there is no seam, and without a seam a folding carton is just a printed sheet.
Where it sits and how wide it runs
It is industry-typical for a glue tab to be somewhere in the region of half an inch to three quarters of an inch wide. Narrower tabs give less bonding area and a weaker seam. Wider tabs waste board and can show through as a ridge on a thin stock. The exact width is set on the dieline against the board caliper and the carton dimensions, which is one of several reasons artwork should always be laid out on the supplied dieline rather than on a rectangle drawn from a measurement.
Which panel the tab attaches to is a design decision with visible consequences. The seam lands on one vertical edge of the finished carton, and on a dark or heavily printed box that edge can show a faint line. Put the seam on the least visible panel, usually a back or side panel, not on the face.
Four rules for artwork near the tab
| Rule | Why |
|---|---|
| Keep varnish and lamination off the tab | Adhesive does not bond reliably to a coated surface |
| Keep heavy ink coverage off the tab | Dense ink film can also weaken the bond |
| Do not place barcodes or critical copy across the seam | The lap creates a small step that can distort a scan |
| Allow for a small tolerance across the seam | A pattern that must align perfectly across the seam will show any drift |
Related features worth knowing
A glue tab is not the same as a dust flap, which is the small flap that folds in first at the top or bottom of a carton to close the ends. Nor is it the same as a tuck flap, the panel that tucks into the carton to close it. And a crash lock or auto bottom base uses glue in a different place entirely, bonding base panels so the carton pops into shape when squared up. If your carton has an auto bottom, it has glued areas at the base as well as the side seam.
Ordering
You do not need to design the tab yourself. Design support is included, the dieline is supplied with the tab, creases and glue areas marked, and a digital proof is produced before anything prints so you can check how the seam falls against your artwork. The die and plates and US shipping are included too. Minimum order is 100 boxes, and pricing starts from about $0.48 per unit at bulk volumes, confirmed on your written quote. Turnaround is stated per product in three lanes: rush with expedited production and air freight, standard by air, cost saver by sea, from about 7 business days, plus 2 to 5 for delivery. Specialty imported items can run up to about 12 weeks. Production is in West Chicago and Guangzhou.
For the wider picture of how a carton is engineered, read what is structural packaging design. A typical tuck end carton with a side seam is shown on lip gloss boxes. Send your artwork and dimensions to request a quote and the dieline comes back with the tab positioned for you.
