can anyone help me??? i've seen it sold all over the place internal stop skim bead for plasterers but i have no idea what its used for..... been told in the past its used for breaking up larger area's for more manage able sizes but then ive been told never to do that as you can see the joining lines????? can anyone once and for all tell me its intended use???????? and any other uses???????? does anyone actually know ??? ??? ???