A 'jigsaw' of hundreds of pieces of steel was presented to workers with no explicit instructions on how to safely assemble it, an inquest heard.
Four men were killed after the heavy metal structure they were working on collapsed at Claxton Engineering in North River Road, Great Yarmouth.
Structural engineer Richard Carr had devised the cage to reinforce the concrete base unit of a high pressure test bay.
But Robert Horner, for the families of the deceased men, asked Mr Carr why no instructions for safe assembly had been provided.
Speaking yesterday, on the second day of a jury inquest at Sprowston Manor near Norwich, Mr Horner described the design as a 'jigsaw'.
'It was a novel design that was being produced,' he said. 'You were designing it from a blank piece of paper.'
Daniel Hazelton, 30, and Adam Taylor, 28, both of Rickinghall, and Thomas Hazelton, 26, and Peter Johnson, 42, both of Stanton, near Bury St Edmunds, died on January 21, 2011.
Mr Carr, who had worked for Scott Wilson Group at the time, said he had envisaged the cage being built in a secure and safe excavation and that there was 'more than one way' to piece it together safely.
He said he had not included instructions for assembly with the design as the manner in which the contractor chose to assemble it could affect costs.
Mr Horner pushed him for details on safe methods of assembly before senior coroner Jacqueline Lake intervened, sparking objections.
A family member shouted 'it's crucial'.
And Julia Kendrick, for principal contractors Encompass, said it was important to know safe methods of assembly as if they involved a crane they would have needed to be costed.
After legal submissions, coroner Mrs Lake said Mr Carr will be producing written statements 'in regard to the design work'.
The inquest continues today.
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