Vertical rods can be affixed to crash bars allowing both doors to be opened with no center clearance obstruction. When the bar is depressed, a chord within the vertical rod gets pulled, which lowers a latch at the top and/or bottom and allows the door to open. The "Pullman latch", which attaches to a Pullman keeper, is the locking mechanism usually used at the ends of the vertical rods. More expensive products may feature vertical rods and latches concealed within the door.