Duct Taped Clips is a Weapon Attachment. This attachment increases reload speed. Two magazines are taped to each other, one upside down, leaving enough space so as not to interfere with reloading. When the time comes to change magazines, the magazine is simply removed, flipped over, and the secondary magazine is inserted, removing the time it would take to retrieve a new magazine. This will only work for the second reload after a new magazine, however. Reload time is usually the same when replacing the spent magazines.
This attachment is also featured in many other FPS games, including call of duty 7.