The Trapdoor Key is a key found in the level Barkhang Monastery in Tomb Raider II.
It unlocks a trapdoor inside the main hallway, which accesses a rocky valley in which lies a Prayer Wheel.
It is found in a difficult area of the level - Lara needs to overcome many continuous traps in order to reach a safe area where the key is located. This area is located at the end of the corridor leading off from the main chamber. Several swinging spiked sacks, burners and deadly rolling blades are among the traps in this gauntlet.