When is directional lock useful?
Four freely swiveling casters are maneuverable but can require continuous steering correction. Locking one or more casters in a forward orientation creates a directional reference. This can improve corridor tracking and reduce fishtailing, especially on long equipment.
What does total lock do?
A total-lock mechanism usually applies a wheel brake and restrains the swivel head. It is selected for parking and stationary use. It should not be described as an emergency or service brake unless the complete system is designed and verified for that purpose.
Selection note
The useful arrangement depends on equipment geometry, operator position, caster offset and the expected turning radius. Evaluate the transition between modes, not only the locked state.