The lower slide is what checks the compaction level with each cycle.
This is the most important part for your machine. The slide has a tendency to wear down after making several, and I mean several cartons of cigs. Simple to install. All you have to do is get the compaction adjusted and you're ready to go.
When this part starts to wear down the tobacco gets stuck and the compaction gets all screwed up. Replace this part and your back on track.