[blam]

"Arrowhead hunting would be a lead-pipe cinch."

Perhaps.

The anthropologist in me wants to know the origin and meaning of 'a lead pipe cinch?'

[Old Professer]

I believe it comes from the use of a solder-type material (lead/tin alloy) that, when slipped over a wire rope and then pulled back over a loop made in the rope and crimped forms a "cinch."

Tip: look at your keychain, there's a good chance it resembles this.