B D Finch Jan 7, 2015:

@Tony Yes, that's also a likely meaning.

Tony M Jan 7, 2015:

@ BDF While I agree that the sentence as it stands is flawed, I had understood it a different way: I suspect it might be meant to read "... and be turned until..."

As ever in this sort of situation, it's anybody's guess, since both scenarios are possible and plausible.

B D Finch Jan 7, 2015:

Grammatical error This should read: " ... must meet in drive direction and turn until they fit tightly.