So, when a Reddit user asked hair stylists everywhere, "how exactly do you want customers to communicate what they want to you? What do they say/do that is unhelpful?" people were ready to vent about their horror stories from the salon. No, you actually have no clue what an "just an inch" means...
As a barber who's made many mistakes by assuming what people want I now ask a lot of questions. Some people are awkward and don't like to talk but I don't care. I carefully and respectfully ask them questions to figure out what they want. Most men aren't picky.
Some men are. Some have no idea what they want. Its my job to guide them in the right direction. I cut a lot of walk in customers and have narrowed down the questions to just a few. Here's an example of how it usually goes.