Abstract: The measuring apparatus consists of a stationary or mobile desk (8) having at least one aligning bar (9) for interaction with at least one of the measuring surfaces (2) of a measuring limb (3) of the sliding gage (7). At least one measuring surface (2) is outside the plane of the graduated straightedge (1), and at least one of the measuring limbs (3) has two limb parts (30) which project in two different directions from the graduated straightedge (1) parallel to the plane of the latter, and whose two measuring surfaces (2) are in a plane perpendicular to the graduated straightedge (1). Means for detachably fixing the aligning bar (9) and/or the object to be measured on the desk (8) may be provided. Preferably, both measuring limbs (3A, B) are displaceable on the graduated straightedge (1), and at least one of the two can be fixed.