From Mettazhagiya Singar Sanctum main entrance, take right and there is a huge mandapam. Proceed straight inside this mandapam, and one can find Lord Vasudevar Sanctum. This sanctum also has a small board which has Periyalwar's Thirupallandu encrypted in it.
This entrance also forms one of the entrances for Aiyndhu Kuzhi moondru Vaasal.
After visiting this sanctum, turn right and proceed a couple of steps straight.
On the ground, there is the Ayindhu Kuzhi (5 holes) with Goddess Ranganayaki Thayar's lotus feet impression.
One has to place his/her five fingers inside these holes, without bending their hand elbow and look at the Paramapada Vasal, when Lord Namperumal comes in procession during Vaikunta Ekadasi Festival.
It is said that, this is how Goddess Ranganayaki Thayar, also waits for Lord Namperumal's arrival.
This Ayindhu Kuzhi represents Swami Nammazhwar's Artha Panchakam, which consists of 5 important things which every human being should know -
What is meant of Jeevatma (Soul)?
Who is the Supreme Personality of Godhead ?
What is the means of attaining the Supreme Personality of Godhead ?
What to do after attaining him ?
What is that one thing that stops from learning and experiencing all these ?
Some misinterpret this to be rasi kuzhi, which is not called as a rasi kuzhi by Aindhu Kuzhi.
The moondru Vasal refers to the three entrances present around the Aindhu kuzhi. Two entrances are present on both sides of the Aindhu Kuzhi, where the entrance that is adjacent to Lakshmi Narayana Perumal Sanctum leads to Sri Ranga Naachiyaar Sanctum, and the other entrance on the other side of Aindhu Kuzhi leads to this Vasudevar Sanctum, which we are worshipping now.