Keys

An unofficial, common fan-made fail-safe key replica, a large number of which were once sold on eBay

A number of keys are given particular importance in Lost by being shown on screen or specifically mentioned:

• The key to the marshal's handcuffs. Kate unlocked one of the bracelets with the key she took from the unconscious marshal, who hit his head during turbulence, in episode "Pilot, Part 2". Kate then dropped the key in the plane when she reached for the oxygen masks. This key was lost in the crash.
• The keys mentioned in Danielle Rousseau's distress message, heard in episode "Pilot, Part 2": "Brennan took the keys." It is unknown what those keys were.
• The key to the marshal's safe deposit box number 815, which Kate used to open the safe deposit box in the New Mexico bank in episode "Whatever the Case May Be". How Kate obtained that key is still a mystery.

Anthony Cooper gave this safe deposit box key to Locke. ("Lockdown")

• The key to the marshal's Halliburton case, in episode "Whatever the Case May Be". Kate apparently took the key from the marshal's wallet. Case and key ended up in Jack's possession for a time. He finally took it off in "The Long Con". Its current possessor is unknown.
• Tom Brennan's keys. When Kate ran from the hospital in Iowa, she said, "I need your car keys," and Tom gave her his set of keys, in episode "Born to Run".
• The key to Helen's place, which she gave John as a six-month anniversary present in episode "Orientation".
• John's set of keys, which Helen took and threw on Anthony Cooper's property, in episode "Orientation". What happened to those keys is unknown.
• The key to the marshal's handcuffs. Kate unlocked the handcuffs she took from the marshal after his car went off the road, in episode "What Kate Did".
• The key Cooper gave to John for the safe deposit box, in episode "Lockdown".
• The key to the fail-safe, in episode "Live Together, Die Alone, Part 1". First seen in Kelvin Inman's possession and later taken by Desmond, who used it.

The key to Hurley's Camaro. ("Tricia Tanaka Is Dead")

• Hurley's dad hands him the key to start the Camaro in "Tricia Tanaka Is Dead".

The key to the DHARMA van brought to Hurley by Vincent. ("Tricia Tanaka Is Dead")

• The key to the DHARMA Van. The key was found by Vincent, clutched in the remains of Roger's hand, and used by Hurley in "Tricia Tanaka Is Dead". Attached to it was a key chain with a lucky rabbit's foot charm.
• Howard L. Zukerman's key, which Nikki and Paulo snatched off his neck after poisoning him, and used to open his hidden safe containing diamonds, in "Exposé".
• Juliet feigned ignorance of being handcuffed to Kate in "Left Behind", but later revealed she had the key all along.