SINGAPORE - The odds of finding a match for bone marrow patients are probably worse than the proverbial saying of finding "a needle in a haystack", because only one in every 20,000 people will be a right fit.

To convey this message and encourage more people to donate their bone marrow, students from Raffles Institution have put together a 1,000-piece puzzle mosaic that is mounted on a wall at the IMM shopping mall in Jurong.

But 999 of the pieces do not fit with one another, with only the last piece being able to do so.

"The one piece that fits shows how hard it is to find a match for bone marrow transplants and with this project, we hope that patients get a fighting chance at life," said Ms Kylie Leong, 16, one of the students behind the project.

Shoppers at the mall over the weekend are invited to donate $5 for the chance to design a puzzle piece that goes up on the wall.

The money raised from the event, which started on Friday and will end on Sunday, will go to the Singapore Bone Marrow Donor Programme. The non-profit organisation, which was started 21 years ago, manages Singapore's only registry of volunteer bone marrow donors.

This project comes under Citi-YMCA Youth For Causes, a community initiative started by Citi and the YMCA of Singapore, which raises funds for social causes.