Using the app appears to be rather simple. Google AR 'Measure' app turns Android phones into virtual measuring tapes. Continuing on this line, can I measure my height with my phone? Repeat this process until you've reached the mark for your height. Then, move the ruler up so the bottom aligns with that pencil mark and mark the new top edge. Mark the top end of the ruler with a pencil.
Place one end of the ruler flat on the floor and position it so it's pressed vertically against the wall.
