When using a fountain pen, angles are important, and it is in this area that most people find themselves in trouble when they first start writing with one. In considering angles, it’s worth thinking of the orientations of aircraft; they are the same general shape as pens, if one ignores the wings, and borrowing the jargon simplifies the task of describing correct grip
Roll: Imagine for a moment that the pen does have wings. Writing, like flying, is much easier if the wings are level, and becomes nearly impossible as they come closer to vertical.

Fountain pens are meant to hit the paper at an angle of a little below 45°, with something between 30° and 60° being an allowable operating range...
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