Green’s Dictionary of Slang

nuts and bolts n.

the basics of a situation, the fundamental issues.

1969		Time 28 Mar. 15: Laird has immersed himself in day-to-day Pentagon business in order to learn the nuts and bolts of the Defense Department.
1970		Sat. Rev. (US) 10 Oct. 64: What of the nuts and bolts of printed news in the years ahead?
1987		P. Johnson History of Jews 433: More than anyone else, he was responsible for the nuts and bolts, the bread and butter, of the new home.
2020		W. Boyd Trio 7: He didn’t enjoy the pettifogging nuts-and-bolts business of making a film, it wasn’t his forte.

In compounds

nuts and bolts man (n.)

an uncomplicated ‘hands-on’ type of person.

1964		Current Biography Yearbook 121: John Dykstra, who calls himself a ‘nuts and bolts man’.
1978		G.P. Gates Air Time 183: Socolow, a man of restless temperament, welcomed the extra action and readily became Midgley’s detail man, his nuts-and-bolts man.
1984		S.B. Oates Let the Trumpet Sound 157: He called King ‘the leader’ and referred to himself variously as ‘Dr. King’s chief-of-staff,’ [...] and ‘nuts-and-bolts man’.
1998		R. Karen Becoming Attached 110: Bowlby was a nuts-and-bolts man. He liked hard data and researchable concepts.
2003		S. Hunter Havana 249: You’re a good nuts-and-bolts man, I give you that. But you have to see a larger picture, see where it’s all going.