While the title of this question sounds like purim-torah-in-jest, this is not my intent.
A Shabbat guest told me then when he was in a yeshiva high school about 20 years ago, the rosh yeshiva required the boys to tie down their kippah with a handkerchief around their head so that the kippah wouldn't fall off while they played ball. They were not allowed to use bobby pins because it was considered bigdei isha (women's wear).
I was surprised to hear this ruling, as this is a new idea to me. Was or is there any opinion that rule or currently rules that bobby bins are bigdei isha?
Your answer can address the usage of bobby pins, in general, but, I'm more interested in its usage to hold down your kippa. Thus, you could address the ambiguity of begged isha. I.e., perhaps an item is normally considered begged isha except when used for a special circumstance.