Dear Rabbi Ari Is בְּעַד meaning replace something with even more of that thing and תַּחַת meaning replace something with equal amount of that thing ? Many thanks, Guy

You are correct regarding "tachat" that it is something in place of something else, equivalent (i.e. money in place of the eye) as is clear from Dvarim 22, 29. But "ba'ad" usually means opposite (e.g. Breishit 26, 8), where the parable in Job means that the leather of the soldier's shield protects and is opposite his own skin, in that it absorbs the blow which otherwise would have been to the soldier's own skin. See the various commentaries there to explain this parable.