The recessed rail closest to the bartender where empty glasses are placed, usually indicating the patron is ready for another beverage.
Just put your glass on the Snead rail when you are ready for another.
The lowered 3-4” railing at the back of a standard bar, usually containing narrow rubber mats to hold liquid from spilled drinks.
When you get done with your glass, set it on the Snead Rail to let the bartender know you are ready for a refill.