I haven't been mapping long either. a few things about this site. Before you ask a question in the forums, please check if it has been covered somewhere else on this site. You can check the forums, tutorials, ect. All you have to do is use the search function on the top right of the screen. Type keywords, as you would a google search, and press enter.
P.S, a ladder is automatically invisable. IT doesn't matter what texture you use.