We went to Ontario for 12 days last summer for a Titanium Rally.
Into Canada at Thousand Islands:
Customs Canada: Passports, please, and may I ask why you are visiting Canada?
Me: Here they are and we are going to a RV owner's camp out.
CC: How long are you planning to stay?
Me: 12 days.
CC: Why do you have that number on the trailer?
Me: It is a Titanium Owner's Group I.D. Number.
CC: Do you have a valid Driving License, Insurance, and shot records for your dog?
Me: Yes, right here.
CC: I don't need to see them. Drive safely and enjoy Canada.
End of border crossing.
Returning at Buffalo was almost as easy. The inspector did open the door of the trailer and stick his head in (while standing on the ground). I guess to see if it was full of those pesky undocumented Canadians.
Have fun.