On the levels with hot air balloons, you need to get them to the grey "hoovers." The balloons are not always lined perfectly so they would go straight up to the hoovers by clearing blocks from between the hoovers and the balloons. Thus, you must move or "teleport" the balloons by making them go through the teleports. 

It's not enough to get the hot air balloons through the teleports to clear them; the teleports are just there to move the balloons to a different location on the board.