
I'm always switching purses or wallets or fumbling and dropping cards on the floor trying to get to the right one. By punching holes in the corner and keeping them on a key ring, I've been able to make sure I have the right card when I need it.
Sometimes I'll put the clamp on the end and attach it to my keys if I'm not carrying a purse. This way I also always have those annoying Macy's or Victoria's Secret coupons that get sent every month. (keeping the post office in business though)