The locking bar is a long parallel flat bar that a perpindicular flat bar connected at a right angle on the top and bottom. These top and bottom pieces have a 90 degree bend at the end that runs parallel with the front of the machine. When the hooks in the door are inserted in the slots on the cabinet, this latch should engage in the slot and lock the door. The lock will mount in the middle of this flat bar and turning the lock should engage or disengage the latches at the top and bottom of the door.
Pardon the less than technical terms but I hope the pictures help it all make sense. There is currently no lock in the bar on my machine. The first picture shows the upper latch. I could not get a good shot of the lower latch. The second picture shows the part of the locking bar where the lock would be mounted. I am not 100% sure that this bar is complete because it did not have a lock when I got it.
Tim