Abstract: Apparatus with a platform or the like and a plurality of adjustable support legs extending through the platform. Each leg is provided with a device at the upperside of the platform which can effect relative displacement between the leg and the platform. Each of these devices takes the form of upstanding support members disposed around the leg and each having a foot plate which engages in a shoe on the platform. Each foot plate and its shoe have inter-engaging curved surfaces constituting spherical joints which permit the support members and hence the device as a whole to perform angular deviations from a vertical position.Hydraulic rams are suspended from the upper ends of each of a pair of support members on diametrically opposite sides of the leg. These rams are interconnected by a carriage which supports a locking mechanism which has a plunger capable of engaging in one of a series of vertically-spaced recesses in a bar of each of the diametrically opposite sides of the leg.