NOVELTY - The system (10) has vertical tilt brackets (16) supported by an underlying substrate. A foldable support array includes a connection interface for the vertical tilt brackets supporting vertically-aligned upper panel rails (30) at connection points. Two diagonal supports are arranged between the upper panel rails. The upper panel rails are in parallel in a deployed position. The array is collapsed such that the upper panel rails and one of the diagonal supports are aligned in a package for motor road transport. The diagonal supports are aligned opposite to each other.    USE - Foldable bi-directional support system for a photovoltaic array of a two-tier parallel solar panel and a panel-like structure i.e. solar energy collection system, for a motor road transport vehicle i.e. lorry.    ADVANTAGE - The system is easily installed on-site, while resulting in precise configuration for mounting the solar panel, thus allowing the system that is simple and inexpensive to optimally position and easily attach photovoltaic panels, while meeting architectural and engineering requirement and maintaining security of mechanical connections of the solar panels to panel rails despite flexing of the panels caused by gravity, vibration and environmental factors. The system allows a panel support structure to be integrated in an easier manner in a wide range of mounting sites and to reduce mounting or deployment time. The system can be easily deployed or removed by rotating intersecting structural units without fouling, jamming and binding at intersections of structural units. The system is easily transported by a motor road vehicle to an installation site. The system can be easily fixed to a hard mounting ground support using bolts without causing damage to the system and can be easily adapted to a wide variety of solar panel array sizes and shapes.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for installing a foldable support array of upper panel rails and diagonal supports to support an array of parallel panels using on-site vertical tilt brackets.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a support system and solar panels arranged in a column in spaced relationship.    Foldable bi-directional support system (10)    Vertical tilt brackets (16)    Vertically-aligned upper panel rails (30)    Panel clips or holders (120)    Tilt-mounting bracket attachment bolts (240)