"I don't know."
"I have no ideas for you."
I like these.
Also, I could not imagine some one just adding a gate to a fence that their neighbor put up!
Where I live, on one side there is a drainage ditch between the fences, and on the other side it's a shared fence. We have discussed with the shared-fence-neighbor about putting in a gate so that our dogs can play together, but we would never assume that it was just okay to go ahead with it without explicit permission.
I have a true story to share:
Years ago a manager of a dental office caught a father cutting the fence that went around the office and installing a gate that matched the fence. When asked what the H he thought he was doing and why didn't he asked the manager was told, "My kids need the shortcut to go to school and I didn't ask because you would have said no".
A police report and restitution (expensive) ensued. If he had only asked nicely I believe the office would have gone along with the plan.
When we moved into the house we mostly grew up in. I was 5 and sis was almost 2. Shortly after people bought the lot behind us and built a house. They had a girl between Sis and me and another one just a bit younger. At this point we just had a chicken fence between our yards. So with my help the others could get over it.
At the time Piney Point had a narrow little bike path set apart from the main road by silver armadillos. This was also before they built the bridge over the bayou connecting San Felipe with Memorial - so lots of traffic from Memorial down to I-10. to go into town rather than winding through Memorial Park.
So our Dad's decide that when they built a proper fence they would put a gate in it so we could play without being escorted from one block to the other.
Fast forward the fence needs replacing. I'm a HS freshman so 14/15, sis is 10 the other two girls were probably 11/12 and 8/9 years old. There is a very nice wide and safe hike/bike trail were the old ditches used to be - very safe. So our parents decide to do away with the gate - in part because neighborhood kids from both streets had bee useing it - worn paths through both yards and were constantly not closing the gate and letting our dog out.
You would have thought our parents had decided to open a house of ill repute from the reaction of other parents. They actually tried to tell my parents they "couldn't" take out the gate because it would endanger their little hoodlums. Then they tried to tell backdoor neighbor they would put a gate from their yard into his - and he said NO. (Backdoor neighbor's yard spanned 3 yards on our street.) Dad and backdoor neighbor ended up putting locks on the gates, even before they replaced the fence.