Rest Room Key
The Rest Room Key is the first key found by Lara in the Wreck of the Maria Doria level, in Tomb Raider II.
To obtain the key, she first has to push and pull the Movable Blocks that block the passage to the over-turned ballroom area out of the way. In a side passage of the ballroom, in-between Glass Shards she then finds an opening in the floor. Underneath is a short passage she can lower herself into. There she finds the key.
The key is needed in the restroom adjacent to the crate-blocked passage to the ballroom. When using it, a tiny chamber with a switch is opened. This switch opens another door to another switch and has to be flipped once before activating the following switch and once after.
Rest Room Key as it appears in the inventory