My statistician has a 3 row by 7 column data lattice. She wants to have what would amount to the x-axis line on each row, but she doesn't want the column borders. Is it possible to do that? This version of the code that I've included turns on all of the borders with the walldisplay=(outline) on the layout prototype. She'd settle for being able to put a reference line at y=0, but wasn't able to figure out how to do that. If she uses walldisplay=(fill) she gets no column borders, but also no borders between the rows.