What is rail liquor?

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Why: On "1001 Rules for My Unborn Son":

39. Drink rail liquor.
A good drink never needs more than one ingredient. Usually ice.

Answer: It's whatever is in the "well," the house pours, the cheap crap kept on the rails behind the bar - not up on the shelf with all the lights.

Source: Chowhound

The More You Know: Other drinking-related rules:

150. Don't get all fancy about your beer or coffee.
165. On a night out with the boys, never be the first to go home.
241. Keep a well-stocked bar.
243. There is no need to tell anyone you are leaving the bar.
It’s called an Irish Goodbye. And it comes in handy.
311. Don't date your bartender.
368. Just raise your glass. There's no need to clink with everyone at the table.
375. Don't pose with booze.
384. All drinking challenges must be accepted.
416. When meeting people out, don't suggest the bar or restaurant closest to your apartment.