(Watching this on a lazy afternoon ...)
When you commented about forgetting a level, I thought "isn't there one on the iPhone?" And lo and behold it took a while to figure out where it's hidden ("Measure") -- there it was. (Obviously it's not in my frequently used list.) I'm irrationally guessing other smartische phones have a similar app.
(And yes, using the phone to level a large format beastie might prove a little less user friendly than a dedicated level of some sort.
)
Anyway, up to your usual high standards for informative video.
Thanks.