This photograph was taken by the author in November 2008.
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It's actually a sign put up in the glass windows just inside the Diamond Horseshoe for their holiday overlay; during the Christmas parties the horseshoe houses "Woody's Hootin Hollerin Holiday Open House", where food and beverage is sold, Toy Story characters appear and Jim the pianist from Casey's plays holiday tunes on the stage. It's one of the best things about the parties.
Anyway, the glass dividers right inside the doors to the Horseshoe which usually are etched with "DH" and little fleurs are overlaid with signs like the one you see which are made to look like wood. They say "Happy trails to All... ...And To All a Good Night!" and face in, towards the stage.
Right now, by the way, the Horseshoe is open as an adjunct to the Liberty Tree Tavern for dinner. Not only has it been beautifully restored, but the massive Wurlitzer player piano from the Main Street Penny Arcade has been brought in and outfitted with a Christmas roll. It warms my heart to see it.
....Since I know the gate well from my tenure in Adventureland Operations, I'll go on and say that this hallway leads between the Tavern and the Horseshoe, twists around past the Tavern kitchen and a utilidor stairwell, and twists around past the Shootin' Gallery to end inside the Adventureland Veranda. It's called the "Horseshoe Gate" and he neatest thing about it s that the themeing from Liberty square extends back into it, with a slate wall and themed door (not seen in your picture) so that from the road it just looks like a small interior courtyard!
15 miles of cables, cut and dyed castle colors, supporting:32,000 square feet of fishing nets, supporting:200,000 energy-efficient LEDs, interspersed with:500 strobes