Answer

If by “sehason” you mean the sinhasan or altar, then the coconut (shreefal) is kept under it as part of the traditional Snatra Puja setup. Jain puja manuals specifically mention placing a shreefal under the altar, and the sinhasan arrangement is explained as symbolizing Mount Meru, the sacred center connected with the Tirthankar’s birth celebration. ( jainfoundation.in)

Explanation

The coconut is kept there as an auspicious ritual item, not as the main object of worship. In Jain puja, sacred materials are arranged to create a pure, respectful, and devotional atmosphere before Bhagwan. In some Jain traditions, coconut pieces are also used among the puja dravyas in place of certain other offerings. ( jainqq.org)

Spiritual Understanding

The deeper meaning is devotion, humility, and readiness to participate in the sacred celebration of the Tirthankar’s life. The arrangement of the altar and the shreefal helps the devotee enter the spirit of bhakti and reminds us that the real value of the puja is the inner भावना, not the material itself. ( jainfoundation.in)

Takeaway

So, the coconut under the sinhasan is mainly a traditional auspicious symbol in Snatra Puja, placed as part of the sacred setup and not for ordinary practical use. ( jainfoundation.in)