Measure
Measurement
In short
Built-in iPhone app for taking on-site measurements when a tape measure is not handy.
Notes
Apple's Measure app comes built into the iPhone. It is good enough for quick site checks — room lengths, opening widths, and rough dimensions — so you can brief contractors with numbers instead of guesses. Treat the reading as a gauge, not something to rely on: accuracy depends on the angle you hold the phone when you plot the points. For carpentry especially, a precise tape measurement is better.