In advance of settlement you need to get together all of the keys, codes, warranty certificates, product manuals and other paperwork that your buyers are entitled to receive once settlement has taken place.  You will have contractual obligations to deliver this material, usually on settlement.  Sometimes that is handled by your representative (for example the Agent) handing over a package of material onsite.  Make sure everything is clearly labelled (for example keys) to avoid annoying your buyers.