Upanayanam

Those who study the Vedas consider that among all sanskara rituals, the initiation rituals of Upanayanam are the most important.
Upanayanam, also known as the sacred thread ceremony. is usually performed at the age of seven or eight because that is the age when a child stops getting the benefits of the karmas of his parents and will have to learn and perform his own karmas. Upa means near and nayanam means going; that is the act of going to a teacher to learn.
The meaning of the word upanayanam can also be interpreted as nayanam meaning eye prefixed with upa- (auxiliary), making for the interpretative meaning: bringing (the ultimate truth nearer in sight).
There is plenty about Upanayanams on Wikipedia.
According to Aapasthambha Maharshi, a brahmachari should not

• Sleep during the day


• Use cosmetics or perfumes


• Have close contact with girls


• Engage in gossip


• Indulge in entertainment


• Indulge in boasting

He should be disciplined, quiet, self confident, tireless, soft spoken and without ego or jealousy. Chanting of Gayatri Mantra regularly gives him the strength to follow the above rules. This gayatri mantra is taught to the brahmachari by the father taking the position of guru, which is known as Brahmopadesam.
The Upanayanm function starts with Punyahavachanam followed by Yagnopaveethadharanam. The Muhurtham is the time of Brahmopadesam.

After yajnopaveethadhaarnam is Kumarabhojanam. Kumarabhojanam is common both for Upanayanam and choulam. According to the vedic karmas, the vatu (the boy whose upanayanam is being performed is commonly referred to as vatu) should be served with rice, ghee and milk without salt or spices. The vatu (disciple) is supposed to eat bland food throughout his brahmacharya (the period during which he is supposed to do vedadhyana) and taste good food only when he enters Grihasthashrama with the vratha ritual of his marriage. At this time he is blindfolded and when he opens his eyes, he is fed neiyappam (from when he starts eating tasty food) and shown the mirror, from when he starts beautifying himself.
During Kumarabhojanam, another kumara who is not yet a brahmachari is made to sit with the vatu and served food. At some places, another brahmachari is seated along with the vatu and also the food served is rice cooked with turmeric powder and dal, along with fried rice pappads.

After Kumarabhojanam is the vapanam, or shaving of the hair for the vatu. The first locks are cut by the father and then by the barber. Usually, this is a noisy scene during choulam, as this is the first time the boy gets a hair cut.

After the vapanam, the boys are given bath, dressed in new clothes and taken to the temple. In the olden days, this bath was given at the stream and the ladies would all accompany them and dress up the boys at the stream side. From there, they come in a procession to the temple. The maternal uncle of the boy is supposed to carry the vatu during this procession. Aarati is done to the boys in all the houses and also they are given a small gift, usually a piece of jaggery, sugar candy or banana. In return, a packet containing a murukku and laddu is given to all the houses. The aarati water is poured on the dhoti of the uncle. This procession goes upto the temple and returns to complete the rituals.

The rituals of Choula karma is almost over after the boy comes back from the temple and the homa and ashirvadam.

Agnimukham is performed and the boy is given all the symbols of a brahmachari. First the boy made to stand on a stone and the father says, “You should be as strong-willed as this stone”.

Then the father ties a long cloth (known as kuttai) around the brahmachari’s waist and prays, “May the Gods give you long life, strength, health and wealth” (In the olden days, the brahmachari was supposed to wear this cloth for 3 days). A cord made of three strings of Durva (Moujibandhanam) is also tied around the brahmachari’s waist, symbolizing the three sections of Vedas which will protect him from all evils. A piece of deer skin (krishnajinam) is also tied around bramachari’s waist, which will make him bright in intellect as the blazing sun. He will be endowed with health, wealth and prosperity. He will become strong spiritually and intellectually.

Then the brahmachari is taught the most sacred Gayatri mantra by the father. He is taught all the rules of Brahmacharya vratha. He is also given Palasha Danda (a small twig of the peepul tree) as a symbol of brahmachari.

The brahmachari is supposed to live on the food he receives as alms by going from house to house. As a symbolic representation of this now forgotten system, the brahmachari asks for alms from his mother and all the other ladies of the congregation.

Followed by Ashirvadam and aarathi, the upanayana karma comes to a happy end.

The brahmachari is supposed to be in a sort of vrata for the following three days, doing all the nityakarmas of the brahmachari but not going out. On the fourth day, a Pranava Sradha Medha Puja and homa is done, when the kuttai is removed and given to the Acharya and the moujibandanam, krishanjinam and palasha danda are also taken from the bramachari. In the olden days, new palashadanada, moujibanda and krishanajina were given to the brahmachari.
The Upanayanam is the most sacred ritual in the life of a boy as all through the ceremony the Guru (father) appeals to the Supreme beings to take care of the boy and give him long life, health, happiness, intellect and lead him through the right path and give him strength to face all odds in life and also mental strength to lead good life and turn back from all evils. It is an earnest prayer from the father, having brought the child up to his adolescent age, to all powers in this universe, the earth, the water, the sky, the ether, the fire, all the stars, all the deities who are the devatas of all the eight directions (ashtadigpalakas), all the vedic scholars and elders of the community and all the pitrus to take good care of the boy from then onwards. And also by teaching him the Gayatri Mantra he makes the boy responsible for his well being and also advises him on the various dos and don’ts of the life, when he is going to be away in the Gurukula in pursuit of knowledge.
This karma has a very powerful influence on the boy and the family, if the purpose and meaning of each ritual is properly understood and followed.
It is one ritual no one should avoid or postpone as it gives the boy great strength of mind. Practicing the Gayatri mantra everyday makes him strong willed, confident, intelligent and pure in his thoughts and deeds.
Explaining the meaning of all rituals will take lot more space and time; perhaps, I should be able to give the meanings of some of the rituals more elaborately some other time.