When going through automatic ticket barriers at railway stations don't put your case through in front of you but pull it behind, or you may, like me, get trapped in the vice-like and painful grip of the snapping flaps. I could not move a millimeter and the strong staff member who tried to free me could not prise them apart and so was frantically pushing buttons to open them while I protested 'This is hurting me!'
Ouch.
I do worry they could injure a child....so take care.