to merge them at the center just select two points and press "S" then "0" and on the left remove doubles to merge at first or last selected, select the two points and press ALT+M if thats what ya mean edit: im a fuckin idiot just saw the date ree i just hadn't seen this thread b4 and saw it pop up in the new post section, so assumed it was new
When you're done with one part you could hit space and type in "remove doubles" and it should remove all the layered vertices
