Grid References.

[ImLostAgain]

My grandson is about to learn map reading skills. Now I just know he is going to ask me to help him and I'm looking forward to it but...
It has been many many moons since I did it and I don't want to let him down. I've had a quick glance at his 'homework' and he has, as far as I can see, been given two grid reference numbers of five figures each.
Now I vaguely remember four and six figure directions but can't remember ever using five, or even ten if we take them both into account.
Does anyone know of any sites that would explain how to do it.
I've tried youtube but it is mostly showing four and six figures.
I've probably missed something simple here so apologies in advance.

[ImLostAgain]

Apologies to you also jj. Yes it does seem strange. I'll check with him later.

[TonyV]

Might be investing with one off these otherwise u can't use map properly cheapest one I can find is
http://www.blacks.co.uk/equipment/103642-eurohike-navigation-compass-dofe.html/505716/?istCompanyId=d92b362f-ac8a-4a8a-87ca-c56eafad7955&;istItemId=raxlammww&istBid=tzlt&gclid=CLmgnc7gpMoCFUyNGwodfqoPeQ