Nails and studs may be required for them (7)

I believe the answer is:

collars

I'm a little stuck... Click here to teach me more about this clue!

'nails' is the definition.
(I know this)

I don't understand how the rest of the clue works.

(Other definitions for collars that I've seen before include "Grasps" , "Ties with them, perhaps" .)

I've seen this clue in the Evening Standard.

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