Deut 21:12Then thou shalt bring her home to thine house; and she shall shave her head, and pare her nails;
This was about captive women being taken as wives. Since Apostolics do not want to be identified with slavery or mourning, and since Apostolic women are never to cut their hair due to the fact that it is a shame for a woman to be shorn or shaven (see
1 Cor 11), it is obvious by this verse that they should never cut their nails either.
However, in today's society, long nails are a sign of vanity. Therefore, filing is acceptable, but again, per the verse above, not cutting. Further, since most fake nails are over 1/8" long (past the quick), Apostolic nails on women should be kept to a length below 1/8" in order to avoid worldliness. To distinguish the sexes, men's nails must be kept less than 1/16"; however, 1/16" shall be allowable because it's easier to pick up things with a bit of a nail, and scratching is made easier as well. Therefore, 1/16" or less on a man is considered "functional nail growth" and is therefore acceptable.