A Yard of Beer Glass, is commonly referred to as a “Yard of Ale”, leading many to believe that its origin was of Early English Pub’s. But, if that were the case, they would be called a “Meter of Ale”. Its unique elongated shape was first invented in the 17th Century to allow barkeeps to pass a refreshing drink to a parched stagecoach driver while sitting high atop his coach, and not forcing him to climb down. The funnel shape at the top was designed as a non-slip, non spill feature. The proper way to fill a “Yard of Beer” is with 16 oz. of beer, and let the foam fill the glass to the top of the neck. A Yard becomes overfilled when the beer or the foam enters the funnel area. Remember that the idea behind this type of beer glass is to have a container that is nearly spill proof and that separates the beer from the foam while being drank from. Over filling them, like this one, is common.
The trick to drinking from a Yard is in controlling the flow once it begins to reach your mouth. Because the beers velocity is hidden by the foam, most beginners end up wearing a great deal of the beer. This is especially true when the air reaches the ball and breaks the vacuum, allowing the beer to careen down the neck at a speed that is equal the now exaggerated slop.
A clue/hint for you: As you raise the yard to horizontal, begin a slight swirling motion, about 6 inches in diameter at the ball. That will slow the velocity of the flow, and allow the vacuum to dissipate from the ball more uniformly. It takes practice to master and it's fun to watch the novices. The best thing to do is to get good at it, then bring it out at a party, and watch your friends try it. It looks even more impressive if you can dispense the Yard using only one hand, plus it gives the illusion that you are drinking much more that 16 oz. of beer in one fill.
A full Yard of Beer measure about 36 inches, hence the name. There are Half Yards available, they are about 17 inches tall, but they are about 1/10 of the novelty, fun and usefulness of a full Yard. Some Half Yards are called full Yards but they are 17 inches tall with twice the diameter (same volume, half as tall, still 1/10 the fun).
The Official Guinness World Record for drinking a Yard of Beer is Five Seconds, but that was done using an over filled Yard (filled to the top with 1.2 quarts).