A young man goes home from a war to see his mother in the hills of West Virginia. She has never left the hills and has never seen anything like her son's uniform or gun. He shows his mother both items, then she asks about the grenades on his belt.
He says, "Well, you pull the pin and throw it."©OFFICEJOKES.NET

She still doesn't quite get it, so he decides to demonstrate and throws it into the backyard.©OFFICEJOKES.NET

The outhouse blows up and his mother cries, "son you shouldn't have done that! Your father was in there."©OFFICEJOKES.NET

And out crawls his father, all covered in dirt. He looks over at the hole and says, "Good thing I didn't let that off in the house."