I have been to Subrahmanya temples but have never done any piercings myself. I do admire the rare Hindus who do it though. I consider the hooks and skewers as a metaphor for the Vel, an ancient spear which the god Subrahmanya received to vanquish the three demons.
So I consider the piercings to be a symbolic metaphor of understanding and vanquishing the demons of vices within through austerities and spiritual exercises and replacing them with virtues instead. Fasting, mantra chanting (of Panchakshari Mantra), identifying vices and replacing them with virtues, meditation are the spiritual exercises I usually do.
I do like the concept of Kavadi, which is to take upon physical and mental hardships for gaining greater physical and mental strength. And this motivates me to take upon physical challenges associated with rigorous service, long distance pilgrimages to ancient temples, overcoming physical obstacles and others , within my capabilities.
Would you say that your interest and devotion to Subrahmanya stems from a past life !
Ajay: Yes, the piecing needles often have vels, or look like vels. Your interpretation is one I forgot, but yes it is symbolic of His Vel piercing the bondage of ignorance. Past life? Perhaps, although I was in Kolkata. At Palani there was a strong feeling of deja-vu, but Palani is something special on its own. Have you been to Palani? It is where kavadi started. Another interpretation of the kavadi arch is it's the symbolic connector of the pineal and pituitary forces inside the head during nirvikalpa samadhi.
The arch is another whole part of it. I built my own, which is an old tradition. The 3 curving support pieces of wood I used were 3 different saplings from the temple property. Esoterics, you know.