It is a frustration all jigsaw enthusiasts know too well.
Hours spent patiently putting together your latest puzzle can seem wasted when the odd piece goes missing.
For a group in Reepham the heartache is all the more severe.
They have spent the last two and a half weeks carefully constructing the world's biggest jigsaw, only to have lost the final four of the 33,600-pieces.
Children's entertainer Graham Andrew, 48, who lives in Reepham and has organised The Big Jig Challenge, said: 'It's so easy to lose the odd piece and for them to slip in to somebody's bag or something.
'I suppose to lose four pieces out of 33,600 is not that bad really, when you think about it.'
Mr Andrew is trying to find a solution to the puzzling problem.
He said: 'We had a spare jigsaw in case this happened, but each one is unique and the spare pieces won't fit.'
Mr Andrew has been in contact with the jigsaw makers Educa Borras, in Barcelona.
He has sent them parts of the jigsaw around where the missing pieces are and, it is hoped, they will cut new pieces to fit the gaps.
The jigsaw is due to be presented to the Norfolk and Norwich University Hospital on September 15.
Mr Andrew said: 'We were thinking of handing it over with the four pieces missing, but we decided that we need to do this properly.
'The jigsaw will look amazing when it is finished.'
He added: 'There have been lots of comments on Facebook with people encouraging us and telling us not to give up.
'It would have been great if everything could have gone smoothly, but that's just not our story unfortunately.
Are you attempting an unusual challenge? E mail adam.lazzari@archant.co.uk
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