When you crop or adjust an image on NightCafe, the Adjust & Crop preview has two optional overlays. Both sit at the top of the Crop controls. They do not change the saved crop — they only help you line the selection up.
Tap Show Rule of Thirds to overlay a 3×3 grid. Use it to place a subject on a third-line or at an intersection. Tap Hide Rule of Thirds to turn it off.
Tap Show Guides for a finer alignment lattice over the whole preview (evenly spaced horizontal and vertical lines). The lines stay attached to the image, so you can line the crop box up against them. They stay equally visible inside and outside the selection.
Guides are off until you turn them on. You can use Guides and Rule of Thirds at the same time.