You can finalise a visit yourself if you have the Engineer role and are assigned to that visit, by signing it off either on the mobile app or in the web app via the visit's Complete Visit action, which locks the visit against further edits on your device. Completing a visit requires you to confirm all jobs are completed or skipped, provide a worker's signature or tick the confirmation box, and if required, add a counter-signature from a building representative.
The make definitive action to finalise a Location Logbook is a separate step from visit sign-off and is done via the Location's Jobs tab by switching to the Logbook view and generating the signed PDF. This action requires selecting a report signatory (who cannot be yourself) and ticking a confirmation box, and it permanently locks the report once generated. The logbook finalisation is restricted by role and configuration but does not allow undoing; if you need to adjust data after finalising, you must generate a new logbook version.