A retaining mechanism for use in affixing a stratum to bone is disclosed. The retaining mechanism comprises a stratum, a retaining element and a spring element. The stratum comprising a first surface, a second surface, and a hole extending between the first surface and the second surface, wherein the second surface is configured to engage at least a portion of the bone. The retaining element comprises a first position that permits a fastener to be passed through the hole, and a second position that at least partially overlaps the hole. The spring element is configured to engage the stratum and configured to engage the retaining element such that the spring element helps maintain the retaining element in its second position so as to help prevent inadvertent backing out of the fastener after the fastener has been fully inserted into the hole.
