Vishwakarma Puja is usually celebrated in the workplace and always on the roof of the shuktara boys house in Kolkata. Essentially this is a Puja where workers have their tools blessed. This is what Wikipedia says about this festival:
It is generally celebrated on 17 or 18 September in Indian states such as Uttar Pradesh, Karnataka, Assam, West Bengal, Bihar, Jharkhand, Odisha, and Tripura. The festival is observed primarily in factories and industrial areas, often on the shop floor. As a mark of reverence the day of worship is marked not only by the engineering and architectural community but by artisans, craftsmen, mechanics, smiths, welders, industrial workers, factory workers and others. They pray for a better future, safe working conditions and, above all, success in their respective fields. Workers also pray for the smooth functioning of various machines. It is customary for craftsmen to worship their tools in his name, refraining from using the tools while doing so. Modern electronic servers are also worshipped for their smooth functioning.

Special statues and pictures of Vishwakarma are normally installed in every workplace and factory. All workers gather in one common place and perform the puja .

Below are more photos from shuktara's rooftop celebration...