mick wrote on 08/27/10 at 15:06:25:Ok guys,let me put it this way. I am going to to the salt flats next year .if anyone goes I will see you there.If you don't go I don't give a tinkers cuss.
Actually the phrase is "not worth a tinker's dam" spelled like the engineering, not the theological, variety.
A tinker's dam is a little mound of mud put on a pot or kettle being repaired to control the flow of the molten solder going into a crack or pit. I learned this from the Mormon dental students, who would loudly shout out "This project's not worth a tinker's DAM!" while the rest of us would have used saltier, and briefer, language. When I inquired, the above is the explanation I received.
However, even though they acknowledged that "half fast" is a nautical term*, they could never bring themselves to use it in the lab!

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* A line (or rope to you landlubbers) is half fast when a single turn is taken around a cleat or bollard. It's not "fast" (fastened), so it must be tended or you may be swimming after the bitter end!