Which feature is characteristic of an A-frame ladder?

The characteristic feature of an A-frame ladder is that it is self-supporting when fully opened. This means that it can stand independently without the need for additional support, allowing firefighters to work at height without needing someone to hold it in place. This stability is particularly beneficial in emergency situations where quick and safe access is required.

While an A-frame ladder does offer versatility for various tasks, its primary design feature is the ability to maintain a stable, upright position when deployed, making it ideal for reaching higher locations safely. This contrasts with other ladder types that may require angling or an external support for stability.