Abstract: An elongated lengthwise extendible and retractable brace is provided and equipped with structure for releasably locking the brace against retraction thereof. The brace includes opposite end portions for telescopic engagement with coacting abutment portions of motor vehicle seat cushion and seat back portions which are engageable with each other to limit rearward swinging of the vehicle seat back portion to its operative position in which it is used when the operator of the vehicle is seated in the driver's seat. The seat back portion is forwardly swingable to a position abuttingly engaged with the steering wheel of the vehicle. During forward swinging movement of the seat back portion, the coacting abutment portions of the seat back portion and seat portion which limit rearward swinging of the seat back portion to the operative position are displaced apart.