Collection: String and Washer Envelopes

String and washer envelopes — also called string tie or twist-lock envelopes — use a wound-string mechanism over two reinforced card washers to secure the envelope. Unlike adhesive closures, the string closure is fully reusable: unwind, insert, rewind. This makes them the preferred format for office document routing, HR files, legal correspondence, internal filing and any application where the same envelope is reused multiple times.

The range covers over 25 products across over 5 sizes at 160–180gsm paper weight. Available in a range of colour options including kraft, white and manilla.

How String and Washer Closures Work

Two reinforced card or metal-eyelet washers are fixed to the front and rear of the envelope. A cotton or paper string is attached to one washer. To close: fold the flap, wind the string in a figure-of-eight around both washers. To open: unwind the string and lift the flap — no tearing, no re-gumming, no damage to contents.

Benefits of String and Washer Envelopes

• Reusable closure — wind-lock string mechanism opens and reseals without adhesive or damage.
• Secure fastening — holds firmly in transit and storage; contents cannot fall out in handling.
• over 5 sizes — from small DL enclosures through to large C4 formats for document packs.
• Heavier paper weights (160–180gsm) — more substantial than standard envelopes, suitable for repeated use.
• Gusset variants available — for thicker document packs that require a deeper envelope.
• a range of colour options — kraft, white and manilla across the range.

Frequently Asked Questions

What are string and washer envelopes used for?
String and washer envelopes are used wherever a document envelope needs to be opened, resealed and reused multiple times: office document routing between departments, HR personnel files, legal case files, archival storage, internal mail systems and any application where permanent adhesive would damage or inconveniently seal contents that need regular access.

Can string and washer envelopes be posted through Royal Mail?
Yes — string and washer envelopes can be sent through Royal Mail. The string closure is accepted as standard. Apply the postage to the front face as normal. Most sizes will fall into small parcel given the heavier paper weight and typical document contents — weigh the packed item before assigning a rate.

Are string and washer envelopes compatible with franking machines?
Standard string and washer envelopes can be franked on the front face in the same way as regular envelopes, provided the paper weight is within your machine's specification. The raised washers on the rear should not affect franking on the front face.

What is the difference between string and washer and butterfly envelopes?
String and washer envelopes use a wound-string mechanism on card or metal-eyelet washers. Butterfly envelopes (also called coin envelopes) have a centre-opening flap. String and washer closures are the more secure option for document routing and repeated use; butterfly envelopes are more commonly used for presentation and stationery applications.