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. The closure can be opened and fastened again without adhesive, making the format suitable for office document routing, HR files, legal correspondence and internal filing.

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

• Adjustable closure — wind-lock string mechanism opens and fastens again without adhesive.
• 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 for document handling.
• 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 suit document routing between departments, HR personnel files, legal case files, archival storage and internal mail systems where contents need to be accessed more than once.

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.