Abstract: A door panel for covering the open side of a mail box having a series of individual mail receiving compartments, comprising: a peripheral frame and a grid structure consisting of interlocked horizontal and vertical channel members; a first interlocked channel member has an opening and slots defining a pair of oppositely disposed wall projecting portions while a second interlocked channel member has a pair of slots extending from the free edge of its walls to define oppositely disposed tongues; during assembly of the door panel, the tongues are deformingly bent inwardly in the channel of the first channel members to provide a positive interlock between both channel members.