Connector-only blocks are blocks that serve as a connector between other track elements with no other function. They are typically very short, sometimes even with zero length, so the only purpose would be to show some track elements to create a connecting line on the scene where otherwise there would be a gap.
Traffic direction is always bi-directional, speed limits are not assigned. Connector-only blocks cannot have a station, the cannot serve as start or destination of routes, and they don’t have exit signals. Admin or maintenance blocking cannot be set (they also don’t deteriorate!). They cannot be used as a temporary stop in a command to the train driver.
If a train passes a red signal, the occupancy status is updated for every block separately as the train moves, which applies also to connector-only blocks (noticeable only if length > 0)