Catwalk Blades
From WikiRaider
Lara will encounter these Catwalk Blades (Object Name) in The Last Revelation e.g. in the level Guardian of Semerkhet.
These traps are hanging underneath a walkways, till Lara steps onto the spot above. After a very short time they are triggered and shoot upwards, slicing through everything that is on the catwalk above. If you come to a spot with blades underneath just keep moving and get out of the way..