Abstract: An interlocking door seam provides a stronger seam for double doors, making them less subject to attack by prybars and the like. Particularly for central mail stations (CMS) and central box units CBU, double doors present there are subject to attack by prybars and the like that force the locks and allow thieves to rifle the contents of the enclosed mail boxes. Attachment of interlocking door seam to the first edge of the first double doors protects that first edge from prybar attacks. The adjoining edge of the second double door then releasably fits into a convex strip that protects the adjoining edge of the second double door, thereby protecting it from prybar attack. The interlocking door seam allows normal operation of the double doors while decreasing the risk to the central mail station of prybar attack at the seam between the double doors. Flanges present along the free edge of the convex strip provide easy engagement of that free edge.