The operator wears a harness, the Steadicam "vest", which is attached to an iso-elastic arm. This is connected by a multiaxis and ultra-low friction gimbal to the Steadicam "sled" which has the camera mounted at one end and counterbalancing weight (the monitor and batteries) at the other. The monitor substitutes for the camera's viewfinder, since the range of motion of the camera relative to the operator makes the camera's own viewfinder unusable. In the film industry the armature and weight are traditionally called the "sled", as the two units combined resembled a sled in an early model of the Steadicam. The sled includes the top "stage" where the camera is attached, the "post" which in most models can be extended, with the monitor and batteries at the bottom to counterbalance the camera weight. This is how the Steadicam stays upright, by simply making the bottom slightly heavier than the top, pivoting at the gimbal. This leaves the center of gravity of the whole rig, however heavy it may be, exactly at the operator's fingertip, allowing deft and finite control of the whole system with the lightest of touches on the gimbal. The skill of the operator is to keep the desired framing and composition by feathering his touch on the gimbal, while the rig and operator is in motion, and, indeed, when still.