I was reading a article from the Brittish VW camper site. They were describing how to check your belt tension from the crank to the gen/alt pulley. (Note to mods this is a direct tech quote) and here you go:
"Loose as a W**re’s drawers or a tight as a duck’s butt?"
Now that has to be the funniest shade tree expression I have heard in a LONG time!

I think it decidedly beats "Guteentight",and " go till tight and back off a hair" (I cannot believe that word got nicked, but you get the picture.)