Latte31 -I had never thought of that. I know that I use rule of thumb measurement when telling my daughter how much conditioner to use.
She uses way too much and it leaves her hair very limp. I tell her as a rule of thumb to use a dime size amount.
This way she could visualize the appropriate amount that she is supposed to use without actually having to measure it.
It is just like when a person is required to use a pinch of salt in a recipe. We don’t have an exact measurement for the salt but this general phrase allows us to assume that it is about a half of a teaspoon.