I'm designing a user interface where the user will be editing letter templates. I'm wondering what a folder corner (earmarked page) represents in UX design. Thanks!
Icons are subject to a broad range of interpretations by users.
From my understanding, the fold is a holdover metaphor for a physical piece of paper (i.e, creating a document, and the physical property of the document (a sheet of paper once you print it). Without that 'fold' in the current icon, you would have a simple rectangle.
You'll also see this in physical printers, where an extended fold (revealing the lines indicating content) instructs a user which side with the content should be inserted into the printer feed:
Ideally pair an icon with a text label if possible
From the research at Nielsen Norman: Icon Usability
There are a few icons that enjoy mostly universal recognition from users. The icons for home, print, and the magnifying glass for search are such instances. Outside of these examples, most icons continue to be ambiguous to users due to their association with different meanings across various interfaces.
The document icon with a corner fold is quite common, although many also have some lines mimicking some text. But without access to users and the larger context of your app, you might run into some misinterpretation. That is always a concern for icons that don't have a text label.
That's mostly speculation, but,
historically, when choosing an icon to represent a document, they wanted to go with a "blank piece of paper", which, essentially, is just a white rectangle, which is way too ambiguous. So they cheated, curving a corner of it to look more like a sheet of paper.
And now it's way too widely recognised to change it, so they keep using it to represent documents.
The dog ear paper icon represents the concept of "Document" either as a present object (file) or the action of creating a new one ("New document"). It is also used togheter with the pencil to signify "Edit" (as in "Edit document"). Today with higher resolutions it's not uncommon for this icon to show contents (such as the type of document, or logo of a software, for example).
His first attempt was the following:
You'll notice the dog ear is on the bottom left (but already identified as a "Document" icon). An odd choice since a dog ear in a book is typically upper right. In any case a later iteration of this produced the icon we know today:
You'll notice that in both examples the icon refers to the concept of "Document". An "Edit" icon typically overlaps a pencil over this one.
Note: check this for a visual tour through the history of icons.