# How can I subdivide an edge at a specific point on an axis?

Let's say I have a scenario like this, viewed from orthographic X perspective (num3): Both objects are the same length, but the top line is a single, angled edge while the bottom line is flat and divided into six sections. I want to subdivide the top line by inserting a point at the same Y coordinate as the highlighted vertex of the bottom line, without disrupting the angle of the top line.

Subdividing the top edge will insert a new vertex, but only at the midpoint of the edge. With vertex snapping, I can drag the new vertex to the appropriate Y axis coordinate, but this disrupts the angle of the line because it does not affect the vertex's Z axis coordinates. Edge slide is pretty much what I want, but I can't edge slide a single vertex. How can I make this work?

• Double G does not work in this instance? – Allen Simpson May 28 at 16:45
• to move double G works but it's hard to figure out what your trying to do from those screenshots. – Nand 27 May 28 at 16:51

You can edge slide a single vertex. Select it and type GG and then move it: But if the sloped line has endpoints that have the same x coordinates as the bottom line, there's another way:

Subdivide the top line into the same number of segments as the bottom line: Each new vertex in the sloped line has the same X coordinate as the corresponding vertex of the flat line.

There are various ways to select the vertices you want to remove. One that works is to select the vertex you want to keep and then use CTRL+I to reverse the selection: next shift-left-click on each of the end vertices to deselect them: Then type x and select 'dissolve vertices' to get rid of the excess: and you're left with what you want: Notice that I had both lines share an endpoint. This isn't necessary, and what I suggest would work in your example, so long as the two endpoints have the same X value

• g,g is along the lines of what I'm looking for, but not quite. If you use g,g to edge slide and vertex snap to the bottom line's vertex, it does not inherit the same Y coordinate. I can't post an image, but in my example the slid vertex has a Y value of -0.709804 m but the vertex to which it snapped is at -0.666667 m. – sdfasdfasdfasdf May 28 at 17:24
• @sdfasdfasdfasdf the idea in this answer is that i.imgur.com/c48pSP6.png both vertices (2) and (3) are at the same X distance from (1). So subdividing those edges to the same number of vertices will produce edges of different lengths, but same X-lengths. – Markus von Broady May 28 at 18:09

I'd use a knife tool, though you need to create a face for it to work, and then remove created edges... Select edges, F to create a face, K for knife tool, click on one vertex, move up, C for constrained angle, click, ENTER to confirm cut, 2 for edge selection mode, select edges, X remove them... Quite a lot of operations if you don't have a face and don't want to have a face at the end.

After a walk with my dog I got a clearer head and remembered how I actually did that many times in the past: Extrude the vertex to align to along the other axis, then G, G and snap to the edge.

• Oh and I forgot to remove the edge on the left. – Markus von Broady May 28 at 17:01