straddle, and be laterally secured by, the arbor rods. In order to facilitate removal of weights with angle cuts, it is customary to stack the weights in alternating orientations so that the square corners of any weight will be aligned with the angled corners of adjacent weights. This simplifies removal because the square corners of each weight protrude beyond the angled corners of the weight below, serving as handles that can be easily gripped, even with gloved hands. It is customary to apply paint (typically yellow) or colored tape to the weights that counterbalance the batten (pipe) to indicate that they should not be removed from the arbor. As an additional precaution, they may be strapped in with steel strapping. When a dedicated line set carries a permanent load (e.g., main drape, orchestra cloud, etc.) the counterweight balancing the additional load may be treated in a similar fashion. Steel to lead density ratio is 1 : 1.448 Arbors A counterweight arbor is a sturdy mechanical assembly that serves as a carriage for counterweights. In its simplest form, an arbor consists of two horizontal steel plates, a top plate and bottom plate, tied together by two vertical steel connecting rods. Counterweights are stacked as required on the arbor's bottom plate to balance the line set load, with the weights held in place by the connecting rods. A flat tie bar at the rear of the arbor also connects the top and bottom plates. Guide shoes at the top and bottom of the tie bar guide the arbor along tracks mounted to the side stage wall. UHMWPE pads on the guide shoes limit friction between guide shoe and track as the arbor travels. Spreader plates are thin steel plates with holes through which the arbor connecting rods pass. Spreader plates are lowered onto the counterweights in a distributed fashion as the counterweight stack is being built. Typically one spreader plate is placed on top of every two feet of counterweight in the stack. Finally, a locking plate is lowered onto the completed, interleaved stack of counterweights and spreader plates and secured in place with a thumbscrew. Spreader plates serve to maintain consistent spacing between the arbor rods to ensure reliable containment of the counterweights under normal operating conditions. Also, in the event of a "runaway" (loss of control of an unbalanced lineset), the spreader plates will prevent the arbor rods from bending