Veyyavacca means helping others with their works or tasks, the useful and honest ones from the biggest of all to the very least ones. They may help with the washing, carrying water, farming or just giving advice. Veyyavacca indicates the kind hearted people who will help others willingly and some time even get out of their way to do so. Those who offer the help will gain respect and reputation, from which the return favours would be happily given when asked.
Veyyavacca is one of the ten ways of making merit (Dasa Punna Kiriyavatthu) in Buddhism. It is customary for the Buddhists to accumulate this merit by helping the temples with all kind of chores as required such as cleaning, gardening, preparing foods for monks or even giving a lift for people to come to the temple. The temples for the Buddhists are the place of the Triple Gems (the Buddha, the Dhamma and the Sangha), to do things for the temples is doing service to the Triple Gems.
In the Lord Buddha life time, there was a monk named Phra Sanchaiya. He had done many Veyyavacca works in the previous lifetimes and their fruits have benefited him the Arahantship in his last life.
The story from the Tripitaka (Buddhist Scriptures) is:
In one of his lifetimes, in the time of the Buddha named Vipatsee, Phra Sanchaiya was born in a poor family. He rarely had anything to give alms to monks but he diligently put himself to work in tidying up the Buddha’s place, put things away in good order, and did the same to other monks as well. After that lifetime he was only born in the happy realms such as be a celestial being, a king or a rich man.
In this Lord Buddha time, Phra Sanchiya was born in a rich Brahma family. As he grew up he observed that a few famous Brahmins were very faithful in Buddhism so he sought the opportunity to take audience with the Lord Buddha. After he listened to the Dhamma, he attained the Sodapanta and took the ordination. While his hair was shaved during the ordination process he attained 6 Apinya. Finally he became an Arahant. The merit that supported him to attain Arahantship easily was the Veyyavacca he has done in the Vipatsee Buddha Time.
As you can see Veyyavacca is not just a small merit. It can support one to reach Nirvana.