Aw Mike, you will have a degree in RV Mgmt when we are through with you. When your slide is in the "in" or "Closed" position, get a little stool and adjust the slide lock so it fits between the upper lip of your slide and the inside wall of the trailer. The rationale behind the lock is that it prevents the slide from inadvertently opening as you are traveling down the road. The size of the slide on your and my 189FBS makes the need for such a lock somewhat questionable. Some people use them, others do not. This particular lock mechanism is a pain to deal with, but it is probably wise to use it, especially if you are traveling on rougher roads.
I tied a long piece of plastic ribbon on mine that hangs down after the slide is in place. This reminds me that it is there. Otherwise I am liable to forget and try to open the slide with the lock in place.
Enjoy your FF,