Letter-folding

Letter-folding is a means of secret communication used across the Sunscald coast, especially by the region's urban elites. It involves folding the paper of a written message, or letter, a specific way to convey additional meaning. This can either influence the importance of the written message or render the writing entirely irrelevant, with the intended message being concealed entirely in the medium of the letter.
The practice of folding can vary greatly in complexity, depending on the purpose of the letter. In casual or personal exchanges between nobles, any folding may be fairly basic and followed largely out of a desire not to confuse the recipient. Conversely, in important or covert matters, such as military plans, espionage, or illicit activities, the practice can be highly complicated and personalised. While a horizontal fold typically suggests 'please reply at your convenience', for example, more complicated folding patterns could suggest things ranging from 'please forgive me', to 'ignore the contents, visit me in person', to 'kill this messenger before reading'.
In addition to conveying messages in the folds, letter-folding can simplify the receipt of letters. One of its most basic functions is prioritisation. Traditionally, relatively unimportant messages are sent folded lengthwise, while letters which demand attention or priority are sent folded diagonally. These are known as 'flat' or 'pointed' letters, respectively. A recipient of two letters, one flat, and one pointed, then knows to prioritise the pointed one, and may leave a flat letter until it suits them. Conveniently, these folds are usually obvious enough to be felt through their envelopes, meaning one does not necessarily even have to open the letters to know which to prioritise. Some experienced figures can additionally detect far more subtle folds just by touch.

History

With the copious sugarcane available in the northern Sunscald, paper has historically been a relatively affordable luxury, and consequently communication via paper letters has been popular among the higher classes in Sunscaldic society for centuries. It is believed the practise of letter-folding originated from the desire to veil messages in some way, either to keep some or all of the intended message out of the eyes of 'nosy' couriers, rival groups, or letter thieves. As the practice proliferated and the general meanings of simple folds grew gradually more established, letter-folding transitioned from a purely practical and secretive practice into a part of noble etiquette. The eventual introduction of envelopes and wax seals made the made the more secretive aspects less of a concern in casual conversation, but the utility of letter-folding remained even in trivial affairs in that it allowed nobles to communicate certain things without breaching etiquette. For example, writing "I expect a reply" in a letter would be considered quite rude, while folding the letter horizontally to indicate the same thing is perfectly respectful. The covert use of this practice still carries on, however - spies, officials, and those conducting illicit or frowned-upon activities create coded folds to communicate secretly even in otherwise innocuous letters.

Common Meanings and Terminology

While many of these meanings are well-understood throughout the Sunscald, there are some local or regional variations that can cause confusion or annoyance in inter-city correspondences. For example, while in most areas an important message will be folded diagonally while a trivial one will be folded lengthwise, the people of the city-state of Xylos traditionally do the exact opposite. This has led the Xyloan people to be stereotyped as conceited or self-centred in cities they correspond with. It should also be noted that sheets of paper in the Sunscald are usually square, allowing for neat diagonal folds. In addition, many folds discriminate between vertical and horizontal folds - in these cases a vertical fold is one that leaves a vertical crease on the page when the text is aligned the way it would be read. Some commonly understood folds include:

• folded in fess (folded horizontally): "Reply at your convenience." Indicates the sender is expecting a reply.
• folded in pale (folded vertically): "No need to reply." 
• tierced in pale (folded into thirds vertically): "Do not reply." Indicates the sender is very much not expecting a reply, and will not appreciate one.
• quartered (folded horizontally and vertically): rumours, idle gossip. Folded twice to indicate its lesser importance.
• pointed / folded in bend (folded diagonally): Indicates a letter is important and should be prioritised. May sometimes be creased horizontally or vertically to indicate whether a reply is needed.
• triple-pointed (folded diagonally, then each long corner folded up to create three points): Indicates a letter is extremely important, effectively meaning "drop whatever you're doing and read this." Frivolously sending a triple-pointed letter is considered an extreme faux pas, and will likely provoke outrage from a recipient.
• faux-pointed (all corners folded diagonally so they meet in the very centre of the paper, then folded horizontally and/or vertically): A slightly more obscure fold. Though it is shaped like a pointed fold it is technically a variant of a horizontal fold and consequently technically does not imply importance. While it does not have an agreed-upon meaning, it is a favourite fold to indicate the recipient should look for a hidden meaning in the text, as the number of creases once unfolded tends to obscure the exact fold the message was sent with.
• heart-shaped: a love letter. Despite the elaborate folding required, it is a fairly well-known fold due to the connotations, and it is generally held that the more elaborate the folding, the more genuine the love.
• blunted / unpointed (the top two corners folded diagonally so the edges meet in the centre of the paper, then folded horizontally): an expression of hatred, contempt, disapproval, or rejection. One of the few 'polite' ways to send such a statement, and can be put in an otherwise friendly letter so third-party observers won't notice the antipathy. The point can be 'blunted' further by folding the tip of the diagonal fold downwards, indicating hatred but specifically avoiding any connotations of rejection - for example, in 'teeth-clenched' partnerships. Being open, but polite, about your dislike of another person is considered respectful in some Sunscaldic cultures but not others, so the intended intensity of this fold is sometimes misunderstood in both directions.
• caped (the top two corners folded diagonally so the points meet in the centre of the paper, creating a cape-like shape, then folded horizontally to fit in an envelope): an indicator of death, originating from the practice of draping a cape or cloak over the deceased. This is typically used to alert people of a death of a non-immediate relative, news of important deaths will typically be sent with a pointed or triple-pointed fold.
• M-signed (the top two corners folded diagonally so the points meet in the centre of the paper, then the new top corners folded diagonally so the edges meet in the centre of the paper, then folded horizontally, creating an M-like shape): an alleged sign of secret societies meaning 'kill this person'. Due to its infamy, its modern uses tend to exploit its reputation, expecting paranoid messengers to feel around for the M-shape and consequently jettison the message, making it less likely to be delivered. The general meaning associated with an M-signed fold is essentially 'I am sending this purely out of obligation and I want you to know this' and/or 'I didn't particularly care whether or not you recieved this message'. While this is usually a severe slight, it does have its uses - for example an M-signed love or courtship letter might signal to the recipient that it is being sent out of obligation and even convey an apologetic tone.