In Jain worship, a heap of rice (akshat) is used as a symbol of purity, auspiciousness, and completeness.

When we recite Pancha Namaskar / Namokar Mantra, rice is often offered because:

• it is pure and non-living in ritual use,
• it represents auspicious devotion,
• it shows humility and surrender before the five venerable beings,
• and it is used as a simple offering in puja, sthapana, and mandal rituals.

If you meant during darshan/puja, then the rice heap is generally placed as part of the ritual reverence, not as a material offering to satisfy the Tirthankar, but as a means of devotion and discipline.

In brief: Rice heap + Pancha Namaskar = auspicious symbolic offering of श्रद्धा, vinaya, and purity.

If you want, I can also explain the exact meaning of each line of Pancha Namaskar in simple words.