SK
Self-adhesive without strip
Press the two adhesive surfaces together.
Convenient manual closing for ongoing correspondence.
HELP IN CHOOSING ENVELOPES
SK, HK or NK - which envelope closure should you choose?
SK is closed by pressing the surface with glue, HK after removing the strip, and NK after moistening the glue. See the differences and choose your gluing method.
Comparison of SK, HK and NK
HK
With safety strap
Remove the strip covering the adhesive and press down on the flap.
Manual shipping when you want to simply close the envelope.
NK
Gummed
Moisten the adhesive layer on the flap and press it onto the envelope.
Manual closing or selected envelope systems.
The diagrams show the closing principle, not a specific product model.
| Closure | Needs moisturizing? | Does it have a protective strap? | What to pay attention to? |
|---|---|---|---|
| SK | No | No | Check whether both adhesive surfaces adhere well to each other. The closure does not require moisturizing. |
| HK | No | Yes | The strip protects the adhesive layer until use. This does not indicate a specific shelf life: store envelopes according to the manufacturer's recommendations. |
| NK | Yes | No | For an envelope inserter, check the size, flap shape and paper specifications too. The NK code alone does not confirm machine compatibility. |
Which closure will be convenient?
For manual sealing
SK and HK do not require water. In HK you first remove the strip, and in SK you connect two surfaces with glue.
For an envelope inserter
Check your device's manual and specific envelope compatibility. The flap, format, window and paper are also important.
For printing
The closure does not define the print area. Select an envelope variant and check its mockup and options in the calculator.
Is HK stronger than SK?
The abbreviation alone is not sufficient to compare strength. Paper, glue, storage and correct pressing of the flap are important. For important or thick content, ask for a sample of a specific product.
Ask about envelope samples →