At the moment I am working on a feature film. It's something I have been writing since 2008 - so 7 years now, and I am currently trying to get it ready for fundraising and possible interest by producers or something like that. Part of this involves getting the budget as close to reality as possible. And that involves scheduling.
Scheduling means estimating how long it will take me to shoot this film and putting that into some sort of timeframe - 6 weeks, 8 weeks?
Part of the process means using page 8ths. A script page is usually about 8 inches long. So you measure, with a ruler, how much of those inches each scene takes. 1/8th, 3/8ths, 1 and 3/8ths? Once you have that down it allows you to estimate how long it will take you to shoot each scene, using the eighths as guides.