One technique from the tapestry weaving book by Rebecca Mezoff is using a hidden weft when running vertical lines to close the hole. I decided to try it on my current weaving. I picked a strong thread from my stash and before I make a pass with the weft yarn, lay the thread across. As long as I pay attention to the way I lay the thread, the weft covers it, hence giving me a hidden weft and no vertical slit. I have other areas where I will sew the vertical slit when I am done, to be able to compare methods, however, I am a big fan of reducing finish work so this method is very appealing.