Roofing Wishart's Smithy is the latest development in a $1 million project to restore the last remaining commercial building in Cromwell's original main street.
Wishart's Smithy is classified as a category 2 building by the New Zealand Historic Places Trust.
Restoration project director and Old Cromwell Inc manager Elisabeth Williamson said the roof "slotted in a like a Lego set".
Restoration builders Breen Construction had been inundated with donations of old-fashioned lead-head nails, sent from around Central Otago by people who had scoured their garages and tin sheds to find the old nails, Mrs Williamson said.
The specific nails are no longer commercially produced and are needed when working with old tin, such as that being used for the smithy's roof.
Restoration would continue on the building's stonework and exterior before work shifted inside to recreate the Smithy's historic interior facade.
