On the Church’s website for For the Strength of Youth, we find the following:
Immodest clothing is any clothing that is tight, sheer, or revealing in any other manner. Young women should avoid short shorts and short skirts, shirts that do not cover the stomach, and clothing that does not cover the shoulders or is low-cut in the front or the back. Young men should also maintain modesty in their appearance.
I’ve never understood why the guidelines are specific for young women but general for the young men.
At least they are addressing more than sex-related guidelines in reference to modesty:
Young men and young women should be neat and clean and avoid being extreme or inappropriately casual in clothing, hairstyle, and [behaviour].
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Maybe because men can only wear pants and shirts? :D That’s why the rule is so general for them.