Ladder rack is a piece of metal used to guide cable from where it penetrates the room to the point where it drops down the vertical wire manager and then terminates on a patch panel. It is over your head in the telecom room and is called a ladder rack because it resembles a ladder. It is rigid so it is also used as seismic bracing for the 2 post or 4 post rack. You just span it the full length of the room from wall to wall and attach it with a foot kit at both ends. Then using a top plate you attach it to the rack.