The Arris rails on my fence need to be replaced. The set up is 2.5M * 2M concrete posts cemented in place with 3 arris rails between them. These posts have oblong holes into which the arris rails, having been shaped to fit , have been placed into. Each side reaching in half way. I assume when originally fitted the post arris rails post system where set up serially, in that as each was fitted it was cemented in place. My Question is as the posts are already cemented in place. What is the best way to replace the arris rails and fit new ones to them? Each rail is in the order of 3 metres in length, is there enough "give" in them to bend them into place without dislodging the posts? I am asking this , as I do not want to purchase the materials to do the job then find I need to use a different type of fencing system.