Let say that you have two lines in the same plane
that are not touching but part of the same object.
Now you want the two lines to intersect which means creating a vertex
or do a merge of the tip of one line to the other line at the intersection point of the two lines
How can it be done ?
Tanks & Salutations
Did you try to subdivide the lines and merge the resulting points.
in the edit mode press W select sudivide. select the points you want to merge press W select merge 
Subdivide does not put the vertex at the intersection of the two lines !
You wold end up with three lines instead of two !
Salutations
Have you tried the replys on the post where you already asked this question https://blenderartists.org/forum/viewtopic.php?t=61855&highlight=
This seems like something a Python script could handle, but I have not been able to find any. The maths is not all that difficult. Perhaps you would have better luck finding one.
There is a kludgy workaround. Essentially you want to extend both edges all while keeping one end fixed.
Press the . (period, full-stop) key to make rotation and scaling occur around the cursor.
In Edit mode, select the fixed-end vertex of edge 1. Snap the cursor to this vertex with Shift-S.
Shift-select the vertex at the other end, use S-key to scale the edge. Scale to about where you think the lines will intersect.
Note: If you do not want to deform the mesh, you will have to create a new edge on top of the original.
Repeat for edge 2.
Now the kludgy part; you’ll have to zoom in and continue the scaling procedure. Fiddle with the endpoints until they overlap (use N key to watch coordinates in the Transform window).
When you are satisfied, select both endpoints and Alt-M to merge them at the intersection.
If anyone has an easier, more accurate way to do this (eg has actually taken Descriptive Geometry) please let us know.
I do remenber and i got that on a note file
but t is so cumbersome there must be another simpler way !
Sliding a vertex on an edge fine but so darn complicated!
i don’t understand why there is not an easier way of doing it ?
you can select a vertex and move in 3D but not along the line your in the 3D space
Blender has an edge slide but no vertex slide !
I’m working on a model of the crawler for the space shuttle
and i did the Cabin by starting with a simple plane that i shaped into the full cabin
one problem is that when you cut one edge it has the habit of adding a lot of other edge in other surface around and then you have to remove those extra diagonal edges ect…
but when you have a lot of these knife you can cut yourself ouch !
and it become such a tedious work to cut so many edges to make the windows.
Salutations