- Counterbalance components involved
- Spring count, shaft arrangement, drum type, cable dimensions, bearings and bottom fixtures determine which tensioned parts must be controlled, replaced and reset together.
- Extent of impact transfer
- A dent confined to one section differs from force that also bent an end stile, roller, guide rail, jamb bracket or supporting anchor.
- Lift and track configuration
- Standard, low-headroom, high-lift and vertical-lift arrangements use different track geometry, drums, cables and access methods, so the installed configuration shapes labour and parts.