Making an edge parallel with another Edit: Changed the screenshots and some of the descriptions to be clearer

I was trying to make an edge parallel to another according to the slow, accurate way stated in this page: How to extrude a face parallel to another?

However although the vertex aligned itself with the pivot point, it went downwards, distorting the edge it was subdivided from.

I'd like to have all the bottom edges stay parallel to each other, i.e the parallel with the edge marked with red colour. The subdivided vertex, however, creates an angle on the now separated edge after aligning itself with the pivot point.


The edge I'm trying to create is marked blue in colour, and I need it to be parallel with the green edges while allowing the red edges to remain a straight line. The yellow point would be the subdivided vertex.


I need it to behave like a sliding vertex along the edge while parallel to the frontal slope (i.e the green edge marked above). Simply sliding the vertex won't work because I don't know if it's parallel with the green edge.
It's difficult to see from your screenshots, but what you may need to do is apply the object rotation and scale before you add that extra vertex.

Try this:


come out of Edit Mode and enter Object Mode again 
with your object selected, hit CTRL+A
now select Rotation and Scale
enter Edit Mode and try again


Without this, Blender will often produce unexpected effects when editing the object further, particularly if you've scaled a primitive in one or two axis before editing it.

Good luck!