Salsawazaaa

Hello all. I have a question about the map editor and the world objects So, my problem is that some objects cant be selected, i dont know why... Is there anyway to remove an object with some commands or any special key to press ? The object i wanted to remove is this fence http://imgur.com/xOMeYlr But it also happens with some other objects... is it not removable at all? thanks for your time