Contours and grid lines
Following on from scale bars: contours and grid lines are the other way of letting a reader take measurements off a model without you annotating every feature.
The map grid draws lines at a spacing you set, in project ground units, with separate intervals and colours for the easting and northing directions — so the grid says both how far and which way. Contours follow elevation instead, and read like a topographic map draped over the outcrop.
Both are display options rather than objects: they cost nothing, they do not appear in the tree, and they can be switched off for a clean capture.
A grid dense enough to be useful on a 20 m cliff is unreadable on a 2 km ridge. Set it from the scale of what you are showing, not once for the project.
The settings are under Map Grid in 3D View Display Options.