Then again, it also depends on where you are.
I've flown out of one airport, arrive at another. Go outside for some fresh air because of long layover. Get back into airport, go thru security check, only to have the things in my backpack taken from me. Don't understand it. If it's allowed in one airport, then why not ALL of them?
I've also had little sewing kits taken from me. You know the kind...has a couple needle, needle threader and some thread wrapped around a small piece of cardboard. The entire kit is no bigger than a business card.