Abba – I think Golfer’s point (and mine as well) was that we have heard that there might be a problem sticking your hand in the wall, since at some point past the beginning of the wall is an area of Kedusha. Since we don’t exactly where this point is, we have to be choshesh that it can start at some point past the beginning.
I don’t know if there is a basis for this or not and I think Golfer also wasn’t sure.