What characteristic of hasty harnesses makes them prone to falling off if not secured properly?

Hasty harnesses are designed to be quickly put on in urgent situations, prioritizing speed and ease of use over security and fit. The characteristic that makes them prone to falling off if not properly secured is that they can be constrictive. When a hasty harness is constrictive, it may not fit snugly enough against the wearer's body unless adjusted correctly. If the harness is not tightened sufficiently or secured in a way that keeps it in place, it can shift or slide off, especially during movement or as a result of an external force. In critical rescue situations, this could potentially lead to a dangerous fall. Therefore, ensuring that the harness is snug and securely fastened is essential for safety in rope rescue operations.