I have a photo that I'm cropping to a 6:2 ratio which is fine. However when I move the crop tool vertically I can't figure out how to constrain it so it only moves vertically and not horizontally. I would expect holding shift while dragging would restrict movement to one direction only.
What happens is that I move it vertically to where I want but inevitably I have shifted 1-2 pixels to the side and now have an white bar on the side after cropping.
How can I do what I want?
the vertical sides of the grid will now snap to the vertical edges of the image making grabbing the centre of the grid and moving it (just) up or down a lot easier.
Note: Increasing the Screen Tolerance value will make the snapping more powerful (the blue arrow in my screenshot)