Vertically adjustable support for semi-trailer or similar

The trailer support whose height can be adjusted comprises telescopic outer and inner tubes. The inner tube can be moved inside the outer tube by a spindle (17) with a cogwheel (28) mounted on its upper end. This cooperates with a second cog (30) mounted on the drive shaft of a motor (29) fitted with a cut-off which stops movement when the support contacts the ground. Alternatively the drive may be manually operated.