A seat or seat cover having an integral or detachable upwardly extending wall subassembly particularly advantageous for use on a vehicle seat to prevent items from falling into the gap defined by the seat and console of a vehicle and the gap defined by the seat and door of the vehicle. The seat preferably has a flap installed thereon to which the wall assembly may be attached and detached. In another embodiment, the flap may conceal an area on the seat adapted to secure to the wall assembly. A seat cover may have an integral wall subassembly on one or both sides secured to its seams. In another embodiment, a conversion kit for seats which do not have flaps is provided wherein a securement means may be attached to one or both sides of a vehicle seat and said wall assembly attached thereto.