Without entering a lot of reteric about the many factes of Chakras I will try to assist with the especifc question.
Each chakra has a synbol;
The Crown; 1000 - petaled Lotus
Third eye; 96 - petaled Lotus
Throat; 16 - petaled Lotus
Heart; 12 - petaled Lotus
Solar Plexus; 10 - petaled Lotus
Lower Abdomen or;
Sacral 6 - petaled Lotus
Root 4 - petaled Lotus
Each chakrs has its own purpose, association and connection
Balancing the chakra is not only beneficial to the well being but also the only way of uniting the individual Soul with the Universal Soul.
As a Reiki Master before each healing I open the chakras of a patient before I start to place my hands on my patient and when I complete the session I again check that the chakras are open, suck out any negative energies that may be present then close the chakras.
It is not necessary to use a chrystal to do any of the functions of opening or closing except when a chakra may be difficult to open.
Much other information exists about chakras; eg
Esential Oil, Related Gem stones, Principle, Direction, Associated body parts, Colour, Element, Effect, Associated Zodiac and Plantes, What is in harmony and out of harmony.
When opening and closing chakras one must remember that the chakras spin Alternate CLOCKWISE for a Male and Anti-clockwise for a female
That means For a Male; Crown; clockwise. Third Eye Anti-clockwise; and so on down.
Hope that this posting answers most of your question.
lenny