[Help] Dog won't walk past a certain point?

Hi all! I am a dog walker, and I have a question about one of my furry friends.I have been walking this dog everyday for a little over a month, and everything has been fine until about a week ago.Recently he has refused to walk past a certain point. We will leave his house, go to the right, and about 4 or 5 houses down he will stop and turn around. I will tug on his leash to try and get him to keep walking, but he will not give up trying to go the opposite way. After walking back to the house, we will walk to the left. About 2-3 houses down, he will do the same thing. Each time we walk back and forth, the distance becomes smaller and smaller.As I said, everything has been normal up until last week. We used to walk all around the neighborhood and had a great time! Now he refuses to leave the block. Does anyone have any advice? Thank you! via /r/dogs http://ift.tt/2suu09K