The Lens of Truth is an artifact that lets Link see "the truth", and is found in Ocarina of Time and Majora's Mask. The Lens of Truth allows the user to see the truth; that is, to see things that are not normally visible to the naked eye. It shows which walls, floors and objects are fake, and it allows the user to see things such as invisible ladders, platforms, enemies and ghosts.
Lens of Truth Papercraft