When slicing a cut of meat that has a lot of tough muscle fibers like flank steak or skirt steak, you need to slice AGAINST the "grain" so that the meat is tender instead of chewy.
But how do you identify the grain? And what does it mean to cut "against" it?
If you cut with your knife parallel to the lines in the meat, the meat will be tough. When you cut AGAINST (or ACROSS) the grain, you get tender pieces of meat.
Identify which way the grain is running. If you need to cut it into two smaller pieces to cook before slicing it, cut ALONG the grain, using the lines as a guide..
When you're ready to slice it, cut AGAINST or ACROSS the grain, with your knife perpendicular to the lines so you slice right through them.
You can cut slice the meat into strips before or after cooking it. The grain is harder to see once it’s cooked, but it’s still there!
The piece on the left was cut AGAINST the grain. It’s tender and easy to chew. The piece on the right was cut ALONG the grain. It’s tough and hard to eat!
if you are not sure if you did it correctly, stretch the slices, and you'll see that meat sliced against the grain is springier.