''Azhuvetti Kallu'' at Thrikodithanam Mahavishnu Temple, Kerala - a warning to people not to enter the temple after last prayer (puja)

Azhuvetti Kallu at the Thrikodithanam Mahavishnu temple,Kerala Wikipedia
Thrikodithanam Mahavishnu temple,Kerala  /en.wikipedia.org/wik

Puja or Pooja (in Tamil pooja or poosai) is a  devotional prayer ritual  performed by Hindus as part of  worship to one or more deities.  ''Puja'' is a ''Sanskrit'' word meaning   reverence, honor, homage, adoration, and worship. Puja, the reverential display of deepa  (light), flowers, and water or food to the objects of divinity is a sacred and indispensable  ritual of Hinduism. The worshiper invokes the divinity in the image by saying a prayer and the interaction between the human and the deity, between the human and the guru, is called darshan  (seeing with devotion and respect).  In Hindu temples, the officiating priest does the Puja right before the deity and put in your wishes by being an intermediary and  prays for the welfare your family by chanting mantras. He has the authority to enter the sanctum where the god is enshrined. In Kerala temples, the tradition is the chief priest is called Thantri and his assistant is Melsanthi.  Except them nobody can officiate the pujas in Srikovil - sanctum. Normally, in all Hindu temples in the south, in particular, Tamil Nadu 6-Kala Puja is common.
For example at Chidambaram temple, the puja timing is as follows:

6.30.a.m: Paal Nivedhyam (Paduka is rvrentially taken in a procession from Palliarai (bedroom) and aarthi is done. 
7.00.a.m. Maha Aarthi
7.45 a.m.to 9.00.a.m.Kalasandhi Puja  ( first pooja of the day)
10.00a.m.to 11.00.a.m: Irandaam Kala Puja (2nd pooja of the day)
11.30.a.m.to 12.00 noon: Uchikaala Puja  (3rd pooja of the day) 5.15p.m. to 6.00.p.m: Saayarakshi  4th pooja of the day)
7.00.p.m.to 8.00.p.m: Irandam Kaalam (5th pooja of the day)
9.00.p.m. to 10.00.p.m. Ardhajaama Puja  (6th and last pooja of the day)
[During the time spatika linga abhishekam, maha aarthi and then Padhuka is taken back to palliyarai (divine bed room) in a palanquin, maha aarthi at palliyarai, chandeswarar aarthi, bhairavar aarthi, Ardhajaama sundharar aarthi will be done]. 

After the last puja, the temple is closed for the day (in local language 'Tamil' it is called Nadai Saaththuthal). The temple will be open for Darshan in the following morning.

After Arthajaama Puja 9 to 10 pm, the custom has been that in all Hindu temples, the Garbagriha and all shrines are closed and finally the main temple entrance is closed for the day and the temple will be open on the following morning. The belief is that the deities are like humans taking rest  having spent long day, blessings countless devotees and accepting  Puja  and Deepa Aarathanai every now and then. In most  temples, the main God will be taken  to the palliarai (divine bed room) where the presiding goddess will be waiting for the lord. This is normally done with reverence to the accompaniment of music. In accordance with the temple customs and tradition, the temple should not  be open once it is closed after the last puja - Ardhajama puja. If somebody does it, the belief is it is a sin and will earn the ire of the deities of that temple.

At Thrikodithanam Mahavishnu Temple (also known as Adbhuta Narayanan Temple, located at Thrikodithanam in Changanacherry, 25 km from Kottayam,  Kerala  built during the reign of the second Chera Empire in 800 AD there is a small stone  pillar between the pond and the eastern entrance of the temple, near a public platform for arts and discourses. It is a  strange piece of granite   erected upright on a  stone pillar about six feet high. It is called Kazhuvetti Kallu-  On it you will find the image of a human body -Thrikkodithanam-Atma Nirvana  His waist rests on the pillar, rest of the body is unsupported. He holds a shankhu (conch shell) in his left hand and wears the sacred thread suggesting of his caste- Brahmin.

A question may arise as to the purpose of this stone piece in a holy place. What has  this strange piece of stone  with an image of a human body on it got to do with this  Pandava temple built by  Sahadeva. 

The small column of rock  is a stern  warning that  bribery, cheating and any dishonest act  cannot be tolerated when dealing either with the divinity or tampering with certain age-old temple customs and traditions. Anybody who does blasphemous act would earn the wrath of god   and face severe consequences just like a man lying on the stone pillar.

Once a well-known Nambuthiri Brahmin , the ruler of Chembakaserry kingdom was proud of his prosperous  kingdom and the popular Sri Krishna temple.  In those days temples, being centers of divinity and spirituality,  played a pivotal role in the progressive growth of a country. The Nambuthiri ruler, being jealous of  the ruler of Nanrulainattu (capital-Thrikodithanam), wanted to cause embarrassment to him. What he did was not palatable as it was concerned with divinity - a place of public worship. H managed to make  a deliberate and untimely visit to the famous Vishnu Temple at Thrikodithanam,  knowing well that the temple was closed for that day after Seiveli puja (Aardhajama puja) - the last puja. He bribed the caretaker of the temple. When the ruler of Nanrulainattu came to know about it, he was in rage and finally had the gatekeeper beheaded. Soon the Nambuthri ruler also fell sick and later died.

So, this stone figure was installed near the temple entrance to discourage any  future offenders and others of the consequences of disturbing the gods after the temple is closed at night. This stone symbolizes jealousy, indiscretion and  retribution  and stands as a mute reminder of dire consequences if people  are purposely   engaged in undharmic act.