What is the shortcut for putting a grid over an image that you're developing so you can tell if the horizontal lines are horizontal and the verticals are vertical?
You can turn on the Guides on the Image. Go to Loupe Overlay >> Guides and then you can toggle it using Ctrl+Alt+O Or Command+Opt+O.
Refer: Grid Overlay Options in Lightroom 5 « Julieanne Kost's Blog
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