Abstract: A deposit box construction is disclosed wherein vertically adjacent deposit boxes are interlocked in any combination to provide a deposit box installation having any desired mix of box sizes. In the preferred embodiment, each box door is grooved to receive a metallic strip member that is slidably disposed within juxtaposed grooves so that vertically adjacent doors are rigidly interconnected by the strip members. The interlocking means further includes a flat, preferably metallic plate member that is fixedly secured at longitudinally opposed ends of the adjacent doors. Thus, one strip member and one plate member interlock two vertically adjacent door members to provide a single deposit box of twice the capacity of a single box. A larger number of vertically adjacent doors may be similarly interlocked by n-1 pairs of strip members and plate members.