for a variety of commercial reasons , it may be necessary or desirable that the secured party with a possessory security interest temporarily release possession of the collateral to the debtor . since the release is of a short duration ,it would be cumbersome to require filing .The Code therefore provides that a security interest remains perfected for a period of 21 days without filing when a secured party having a perfected security interest releases the collateral to the debtor. this grace period applied only to instruments, negotiable documents ,and goods in the hands of a bailee not covered by a negotiable document of title. this is one example of automatic perfection ( perfection by simply creating a security interest , also called perfection by attachment ).