nuts and bolts, the

Idioms  

1. The essential or basic aspects of something, as in They have lofty goals but don't specify the nuts and bolts of how to achieve them. This expression alludes to basic working components of machinery. [Mid-1900s]

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Example Sentences

It is interesting to consider that the body – its nuts and bolts, the raw mechanics of it – had by this point long been considered a proper subject for artists.

From The Guardian • May 17, 2016