Most of these machines are of the gantry type, where two vertical columns support a horizontal beam, which supports the measuring probe. There are many other designs in use, however. The bases of these machines are frequently made from granite surface plates.
The simplest machines are manually operated, but more sophisticated machines are moved in a manner similar to an NC mill, and can be programmed to scan over a part and determine the exact center of a large hole or the 3-D shape of some area of a part.