We have about a dozen stock deckles for making envelopes and cards, which fit either our 8½×11″ or 11×14″ polyethylene moulds.
The envelope deckles make a cross-shaped blank which can then be folded and glued to make a straight-flap envelope. The card deckles make a card designed to be folded once to fit one of three of our envelope sizes; each card has two forms depending on whether you want the card folded the short way or the long way. We also have three other envelope sizes with no corresponding card for some commercially standard sizes.
Although you can use these with our plain moulds, we recommend using a ribbed mould. This is especially true for the envelopes, where pulp running under the edge of the deckle can make it difficult to find the correct fold locations.
For assembling the finished envelope, first fold the two side flaps, then the bottom flap. Glue this with some suitable paper adhesive (for instance our PVA Glue). Form the crease for the top flap and apply a strip of a re-wettable adhesive (for instance our Envelope Glue) and allow this to dry. This works best if you have a rectangular template and pre-form all the creases with a bone folder; the template should be smaller than the envelope size by the thickness of the tip of your bone folder.