GAW: “I personally never got the signs, because what if someone sitting down has their knees showing even after the extra four inches? I’ve also seen 10 CM, and those are not the same as 4 inches, which shiur is it?”
My undertanding is that what the Rabbanim are saying is that 4 centimeters is the minimum that could possibly be okay for any skirt for any person. But it is not always enough, since some skirts/people may require more. Generally speaking, the straighter the skirt is, the more material it will need to ensure that knees are always covered.
Additionally, if someone crosses their legs, they need much more material and people don’t always take that into account when shopping (or they kid themselves into thinking they will never cross their legs, and then they do).
It always bothers me when people talk about the 4 inches as though the halacha is that your skirts have to be 4 inches below your knee. That is not the halacha! The halacha is that you knees must always be covered at all times, and that is impossible with a skirt that is less than 4 inches below your knee. (at least that is what I’ve been told. Personally, I have never measured a skirt). But it is assur to buy a skirt that is 4 or even 5 inches below your knees if your knees will end up showing.
Personally, before I buy skirts, I take a chair and put it in front of the mirror and sit down and cross my legs and see if my knees show or not. I also try to look in the mirror to see how the skirt looks in both the front and back when walking or standing, because sometimes skirts are shorter in the back. Sometimes, I ask the saleslady if I can wear the skirt outside so I can see how it is getting into the car.
I didn’t know that 10 centimeters was not the same as 4 inches. It probably started with 10 centimeters since they use centimeters in EY, and then they rounded it off for inches. Do you know how much 10 centimeters is? And are you sure 10 is what they say for centimeters? (as I said, I have never paid that much attention to these measurements).