Summary: To apply line labels and sub-line labels to your RoofSnap sketch, tap the "Edges" tab on the bottom of your screen, select your desired label and sub-label from the drawer, and tap the line you wish to label.
Watch the video below to see the process:
Note: Labeling the lines of your project's drawing allows RoofSnap to apply pitch and calculate the correct measurement. Be sure to label ALL lines for accurate results.