This event is more than a symbolic gesture because by handing over the keys to the property, the vendor hands over the physical possession of the property to the purchaser.
The keys to the property are usually handed over after final settlement, i.e. when the vendor has been notified that the transaction has been finalised by the settlement agent/solicitor and the settlement agent/solicitor is in receipt of the full purchase monies.
In practice, it is usual for the vendor and purchaser to make prior arrangements for the handing over of keys to coincide with their mutual arrangements for removalists and the like.
This occasionally takes place before the settlement has been finalised, but only by signed agreement and if all parties are confident that a date and time have been arranged for the final settlement and that this will be concluded without any hitches. The careful vendor may decide not to pass over keys however, until official notification of the settlement has been received. Your RE/MAX agent can advise you on this important matter.
Disputes sometimes occur if the vendor is unable to provide keys or remote controls (usually 2 for double garage) for every lock on the premises. It is fair to ensure that all keys are provided and this will help ensure a happy transition.