You probably misheard, in which case the phrase should have been "nuts and bolts", as others have already said. However, if the speaker is of a particular mindset, and especially if they are British, there is a chance that this was done deliberately. It is not uncommon to take a well known phrase and vulgarize it by replacing prominent words with swear words, especially if they sound similar to the words replaced or form a pleasing rhyme. If the original phrase is well known then the modified phrase will be understood, typically with the same meaning, even if the phrase created appears meaningless or off-topic.
One common substitution, unlikely to cause much offense today, is
"odds and ends" -> "odds and sods"
The first version brings to mind a drawerful of unpaired items and off-cuts, while the second version has little meaning. The real value in the second form of the expression is in its vulgarity - something many Brits (and indeed, most non-American Anglophones) relish. In your particular case, it is possible that the speaker intentionally made the substitution:
"nuts and bolts" -> "nuts and balls"
expecting it to be understood as the former, but taking some satisfaction in the fact that both "nuts" and "balls" are slang terms for "testicles".