Bommai Kolu

During Navratri, it is a tradition in many homes in Tamil Nadu and Andhra Pradesh to arrange a "kolu". This is like an exhibition of various dolls in odd numbered steps ("padis"). The kolus could be the elaborate, extravagant ones to the simple, traditional and artistic ones. It is important that the Navarathri Kolu is set up with an odd number ofsteps (usually 7, 9, or 11). Some homes have the tradition of keeping a “Kalasam”. Kalasam is a brass or silver pot filled with water and adorned with mango leaves. A "kuthuvilakku" (lamp) is lit, "kolam"(Rangoli) are made before the Kolu and devotional hymns and slokas are chanted. After performing poojas, the food items that have been prepared, are offered to the Goddesses.
Girls and ladies are invited and they are given prasad (the offering given to God that day), kumkum (red powder), and a small bag of gifts usually containing a mirror, a comb, a small box of kumkum, and fruits. This is also called tamboolam. This is a woman's festival. Celebration of being a woman :)
The dolls kept in the Kolu are mostly those of the Gods and Goddesses depicting mythology. Common ones being Dasavatharam, Ashta Lakshmi. Ramar Pattabhishekam, Meenakshi Thirukalyanam, Murugan and Valli, Krishna in Aayarpaadi etc. A wooden pair of doll (Marapaachi - a pair of a boy and girl), are also kept as these dolls indicate fertility. Kolu does not mean that the dolls are kept only on the steps. Themes such as marriage, school, park, zoo add to the fun and creativity.
On the 9th day (Saraswathi Pooja), books and musical instruments are placed in the pooja and worshipped. Tools are also placed in the pooja - as part of "Ayudha Pooja". Vehicles are washed and decorated, and poojas are performed for them.The 10th day - "Vijayadasami" - is the most auspicious day of all. New ventures and any event started on this day are believed to flourish and bring prosperity. Children are made to write their first alphabet on this day -also called Vidya- Arambham. New art like music, dance etc are started. Proper respect and guru dakshina is offered to the teachers.
At night, after Arti, any one doll is symbolically put to sleep and the Kalasam is moved a bit towards North. The next day, the golu is dismantled and packed up for the next year, and believe me this is the toughest job. Its easy setting the Kolu up but packing is difficult.

So, here I summed the 9 days, that signify so much. Let me know if I missed something.All said and done, I am yet to figure out why the dolls are worshipped and why only on odd number of steps. Answers from anyone?