"A bit of old parchment!" said Fred, closing his eyes with a grimace as though Harry had mortally offended him. "Explain, George." 

"Well... when we were in our first year, Harry -- young, carefree, and innocent --" 

Harry snorted. He doubted whether Fred and George had ever been innocent. 

"Well, more innocent than we are now -- we got into a spot of bother with Filch." 

"We let off a Dungbomb in the corridor and it upset him for some reason --" 

"So he hauled us off to his office and started threatening us with the usual --" detention disembowelment and we couldn't help noticing a drawer in one of his filing cabinets marked Confiscated and Highly Dangerous. "

Don't tell me --" said Harry, starting to grin. 

"Well, what would you've done?" said Fred. "George caused a diversion by dropping another Dungbomb, I whipped the drawer open, and grabbed -- this." 

"It's not as bad as it sounds, you know," said George. "We don't reckon Filch ever found out how to work it. He probably suspected what it was, though, or he wouldn't have confiscated it."

 "And you know how to work it?" 

"Oh yes," said Fred, smirking. "This little beauty's taught us more than all the teachers in this school." 

"You're winding me up," said Harry, looking at the ragged old bit of parchment. 

"Oh, are we?" said George.