Answer:
personification
Explanation:
A house does not have a backbone, but a person does. With this in mind, this quote is using personification.
"Lifting, fastening bulky beams, Building the backbone of a sturdy house..."
(alliteration could also be thought, bulky beams, Building the backbone, but as the question only asked for one I thought that personification was the biggest figurative language being used here!)
Have a nice day!
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- Heather
