Lead Pipe

I am carrying a short length of galvanized water pipe in my truck now to rap on the starter in case it proves uncooperative. Carrying this pipe around brings to mind the old phrase "a lead pipe cinch", and since I've got the internet I should be able to find out what it means. The word cinch comes from the strap used to secure a saddle on a horse's back. It runs under the horse's belly. So cinch means to secure, and with widening usage it becomes "easy", as in "it's a cinch" to do this, that or the other. But where does the lead pipe come into it? I was thinking that it came from using a lead pipe as a weapon, as in whacking someone over the head with a lead pipe would be sure to knock them unconscious. But lead is horribly soft, you might knock someone out with it, but, assuming the pipe didn't just droop in your hands, it would assume the shape of your victims head when you struck them. A lead pipe is just not a good weapon. But then I found this on Answers.com:

An easy type of joint used in fabricating pipe from elongated sheets of lead. First, the lead sheets are formed in a cylindrical shape with a flat overlap perpendicular to the cylinder; then, the flat overlap is folded over and crimped, thereby forming a sealed joint.

This goes back to the original meaning of cinch: to secure. So "a lead pipe cinch" is not easy, but it is secure. It's a sure thing. I found an explanation of how to make pipe from sheet metal, including the part about cinching the seam. I excerpted it from the original page.

Here's a piece of old lead water pipe from Roman baths in Bath, England. You can see the seam along the length of the pipe.