I took a leatherman on a plane back in the 90's.

I remember looking into taking a knife with me, pre 9/11. Even then there were complaints that the standards were not very well defined. One story I do remember was about a guy trying to take a knife through security. One guard held it up, showed it was longer than "three fingers" and refused to let it pass. The guy left, came back through a different line, and had no trouble.