A system for controlling pet access to a pet system having an interior compartment, said system comprising: said interior compartment within the pet system to be controlled; and a segmented door structure that opens and closes to control pet access to said interior compartment, wherein said segmented door structure resides inside the pet system when access to said interior compartment is permitted and, wherein said door structure travels in opposing guide channels positioned at opposite ends of the segmented door structure and, wherein said segmented door structure is formed from a plurality of door panels that are interconnected to one another by interfitting mating formations (100, 101, 102, 104, 105); characterised in that: the interfitting mating formations (100, 101, 102, 104, 105) comprise a first, second, third, fourth, and fifth interlocking feature; and each door panel includes the first, second, third, fourth, and fifth interlocking feature, wherein the fifth interlocking feature spans a full width of the door panel to cover over an adjacent one of the door panels so that there is no accessible gap between adjacent door panels; wherein the first interlocking feature of one door panel connects to the second interlocking feature of another door panel when the one door panel and the another door panel are placed in axial arrangement, such that, as a result of the connection of the first interlocking feature of the one door panel to the second interlocking feature of the another door panel, the resulting door structure cannot be pushed together or pulled apart; and wherein the third, fourth and fifth interlocking features do not allow vertical movement between door panels while the door panels are held in axial relation to one another. said interior compartment within the pet system to be controlled; and a segmented door structure that opens and closes to control pet access to said interior compartment, wherein said segmented door structure resides inside the pet system when access to said interior compartment is permitted and, wherein said door structure travels in opposing guide channels positioned at opposite ends of the segmented door structure and, wherein said segmented door structure is formed from a plurality of door panels that are interconnected to one another by interfitting mating formations (100, 101, 102, 104, 105); characterised in that: the interfitting mating formations (100, 101, 102, 104, 105) comprise a first, second, third, fourth, and fifth interlocking feature; and each door panel includes the first, second, third, fourth, and fifth interlocking feature, wherein the fifth interlocking feature spans a full width of the door panel to cover over an adjacent one of the door panels so that there is no accessible gap between adjacent door panels; wherein the first interlocking feature of one door panel connects to the second interlocking feature of another door panel when the one door panel and the another door panel are placed in axial arrangement, such that, as a result of the connection of the first interlocking feature of the one door panel to the second interlocking feature of the another door panel, the resulting door structure cannot be pushed together or pulled apart; and wherein the third, fourth and fifth interlocking features do not allow vertical movement between door panels while the door panels are held in axial relation to one another. the interfitting mating formations (100, 101, 102, 104, 105) comprise a first, second, third, fourth, and fifth interlocking feature; and each door panel includes the first, second, third, fourth, and fifth interlocking feature, wherein the fifth interlocking feature spans a full width of the door panel to cover over an adjacent one of the door panels so that there is no accessible gap between adjacent door panels; wherein the first interlocking feature of one door panel connects to the second interlocking feature of another door panel when the one door panel and the another door panel are placed in axial arrangement, such that, as a result of the connection of the first interlocking feature of the one door panel to the second interlocking feature of the another door panel, the resulting door structure cannot be pushed together or pulled apart; and wherein the third, fourth and fifth interlocking features do not allow vertical movement between door panels while the door panels are held in axial relation to one another.