Weld not working.......

I make them part of the same object, scale in the verticies so they are practically on top of each other and when i click weld it doesnt happen. I even tried upping the threshold as high as possible with still no results. I'm new at this and this is very frustrating. Can anyone help?

this could be caused by a couple of things, first of all just test it by selecting both the vertices and clicking on 'collapse' instead of weld and see if they jump together. If they dont (and they probably wont if the problewm is what i think it is) then read the following

To weld vertices together they must be on the edge of the mesh i.e. the polygon the other side of the line must be deleted in order for the opposing vertices to be welded. Imagine a cylinder, then imagine removing the top face, only the vertices around the top rim can be welded to another element.

Hope this explains it, if it doesnt let me no and ill post a couple of pics to help you out.

If this isnt what is wrong then can you post an image to let us know your problem in more detail? go to photobucket.com or imageshack.com to post images for free.