Abstract: A platform (1) comprising a fixed structure (2) and a plate (3) movable in translation comprising four corners (4). Each corner (4) of the plate is secured to a vertical translation structure (5) which ends in a counterweight (6). A fixed structure comprises three guideposts (7, 14, 21) which coact with three translation structures (5). A support arm (9) is disposed in the upper portion of the platform (1) which coacts with the fourth translation structure (5). In this way, a fourth guidepost is avoided, so that ready access is provided to the space below the plate. At the same time, the plate is supported at all four corners and so is securely arranged.