The Automatic ROPP Capper uses starwheel indexing to move containers through the capping process.

A Starwheel is generally a disc with custom grooves that "catch" containers as they move through the capping process.   The grooves, fabricated specifically for the containers to be capped, rotate the containers until they are directly under the capping head.  The ROPP Capper capping head then descends to seal the container, which then continues to rotate through the starwheel until it reaches an exit position.  A pin will then release to allow the container to exit the ROPP Capper and procede down the conveyor to the next packaging phase!