Cornerstone: a stone representing the nominal starting place in the construction of a monumental building, usually carved with the date and laid with appropriate ceremonies.
I have been asked what I mean by word of honor. I will tell you. Place me behind prison walls—walls of stone ever so high, ever so thick, reaching ever so far into the ground—there is a possibility that in some way or another I may be able to escape, but stand me on that floor and draw a chalk line around me and have me give my word of honor never to cross it. Can I get out of that circle? No, never! I’d die first!