I want two vertices of editable spline become one. Neither
weld helps: vertices remain separate.
Here is a video: http://youtu.be/bp3OJPeKapc
Disclaimer: I'm using 3DS 2013, and I haven't used 2012 before so I don't know that what follows is accurate in 2012.
To get the vertices to fuse/weld, I did the following: 1) Place the two vertices near each other, but not directly on top of each other (helped to make sure I did in fact get both selected. 2) Select both vertices 3) Click Fuse. 4) Click Weld without deselecting anything. This caused them to become one vertex.
Notes: Upon clicking Fuse, the two vertices move to be the same point, but if you try to move it, it shows that it is really two vertices right on top of each other. I did try manually moving them on top of each other, selecting both, and clicking Weld, but it only worked if they were exactly aligned. I think I remember hearing that there is a setting somewhere that dictates how far away your points can be and still be welded.
Hope that helps!
Make sure that both vertices that you are trying to weld are end points to their respective splines. Sometimes, especially if you are working from CAD data, splines will double back on themselves and what looks like the end point is not actually the end of the spline.