The Plug Mug is simple, yet practical – when you’re done at the office for the day, simply wash out your cup and remove the rubber stopper mug valve. Then just leave your coffee mug at your own desk, out in the open for all the office to see. This way, when some jerk your supervisor decides to take the coffee mug off of your desk when you are gone, they will see the hole in the side of their cup and put your cup back on your desk. Or (if your lucky) they won’t notice and by the time they try to fill up your coffee mug they will learn a lesson the hard way – and spill hot coffee all over their own boss! Who knows? Maybe you were the next one in line for his job! So not only did you just protect your own mug – you just got promoted – just for buying a coffee cup!