When I get a corned beef sandwich at a restaurant usually the meat has a grain and is kind of stringy. However, when I buy corned beef at a supermarket it smooth and looks similar to roast beef. What is the difference?
In addition to the direction the corned beef was sliced, you need to boil the corned beef just below a hard simmer -- not on a hard boil. I have relatives who crank the knob to 11 and boil the thing into "stringy meat toothpicks", and that's no matter which way you cut it. I cook a 3 pound corned beef in 1 gallon of water on just a hard simmer for about 4 hours and get fantastic results.
This may be due to the direction in which the corned beef was sliced. In order for it to look smooth, it must be sliced against the grain. If you want stringy corned beef ( sometimes called "pulled corned beef"), you cut it along the grain. You can tell which way the grain is by the lines on the top of the whole piece of meat.