Sandstone Retaining Wall Blocks Fence On Top Of Retaining Wall?

Fence on top of retaining wall? - sandstone retaining wall blocks

I searched this site and could not be the right answer. I have a 3 meter high rock wall on the back of my property. My neighbor made me cm behind a wall 3 meters, so I had my wall about 6 from the line (the property) to secure and make my pass code. I lost a built 6-10 "on my wall, and I hate it, more space, a clearing close to losing another 6 inches or more of the wall is. It is possible to weld positions sandstone? Maybe an iron gate Lock?

TIA