Developer building fence next to our 4plex, too close?

[Mark Hu]

A developer is building a cinderblock wall next to our 4 plex. The property line on his blue print looks like it would give us decent space between the fence and our building. However if they build the wall closer than the blue print, it will be bad news for us.

We are looking for a way to find recourse in case by accident/intent they build the fence closer than they are telling us now. We asked for a "Certification of Property Line", which is supposed to protect us, and the developer agreed to give us. But we called the Orange County recorder, asking how to record it, and they said they don't know that form. Have any of you used a "Certification of Property Line"?