Replacing a featheredge panel in a concrete post?

[DaMekon]

Looking to get some new fencing, and wanted to go for the featheredge/closed board fence, but use concrete posts rather than timber.

Not knowing much about the construction of these at first, I had assumed I would simply get framed ones that would fit into slotted concrete posts. However, these aren't really secure and can be lifted out fairly easily, which is great when replacing them, but do allow easy access to your property.

I then found out that rather than using framed ones, they can be built on site and fitted to concrete posts that have holes in, so 2 or 3 horizontal timbers can be fitted in, then the boards fixed to them. I liked the sound of this, but then thought how do you go about replacing these as and when you have too? The concrete posts wont move to be able to get the horizontal timber out, and if you cut it, how do you then put a new one in?

 

[footprints]

The theory is the horizontal timbers, called arris rails, are cut a bit short of butting up against the next one in the post. So they can be pushed into one post and then slipped out. When fitted they are held central by the nailed on vertical fetheredge vertical planks and sometimes wedges.

Or you can use these.
http://www.screwfix.com/p/mortice-arris-rail-brackets-200-x-65mm-pack-of-10/58168