Is that doorknocker legit?

Very good advice from NZ Police came through this week. In our suburb there seem to be more and more doorknockers. Usually in the day time during working hours. I'm sure most are legitimate businesses or charities but you can't always be sure of their intentions.
Police remind everyone if a stranger comes to your door offering a service, you should always ask to see their photo identification. Don’t open the door to strangers and don’t be afraid to say no. Always keep your door locked, even if you are just in your garden.
There have been reports of a man targeting elderly in the day time by offering to fix smoke alarms and then stealing items from his victims after gaining access to the property.  The full article can be found here:

​http://www.police.govt.nz/news/release/police-remind-residents-be-wary-door-knocker-claiming-fix-smoke-alarms?nondesktop