A blindfold is a strip of cloth used to cover the eyes, rendering the user effectively (but temporarily) blind. This cover for the eyes of an individual is to prevent them from observing.
A kidnapping victim, hostage, prisoner, etc. may be blindfolded for the following reasons:
to avoid identification of the other(s)
to avoid identification of the location or route
to make attacking the other(s) and fleeing more difficult, especially if the blindfold can not easily be removed, e.g. because the victim's hands are restrained by handcuffs or a rope, etc.
Blindfold Chess is a way to play chess, whereby play is conducted without the players having sight of the positions of the pieces, or any physical contact with them.
Blindfold chess was first played quite early on in the history of chess, with perhaps the first game being played by Sa'id bin Jubair (665–714) in the Middle East.
While blindfold chess has been recommended in moderation by many sources as a method of increasing one's playing strength, simultaneous blindfold exhibitions were officially banned in 1930 in the USSR as they were deemed to be a health hazard.