Abstract: A support apparatus includes at least first and second legs, and levelling means including: at the lower end of each of the first and second legs a cylinder and piston unit, wherein movement of the pistons of the cylinder and piston units relative to the cylinders permits variation in the length of each of the first and second legs; fluid communication means for establishing at least one closed fluid passageway between the cylinder and piston units; and valve means for controlling the passage of fluid through the fluid communication means. In a first position, the valve means permit fluid to flow between the cylinder and piston units via the fluid communication means such that the length of each of the legs is accommodated to the profile of the ground, and in a second position, the valve means do not permit fluid to flow between the cylinder and piston units thereby locking the cylinder and piston units in position.