Why mirror modifier does not merge? Goodmorning, I am working to imitate the tutorial at this link:
https://www.youtube.com/watch?v=QbSmoZCrP8I

At minute 5:15-5:30 he creates a circle with 8 vertices, deletes 3/4 of the figure and then use the mirror modifier to complete the operation.

I'm trying to imitate him, but after deleting the 3/4 of the circle I apply the mirror modifier but the circle does not close.
My result is:



Instead in the original tutorial the circle is:



I don't understand where is the problem.
First he added a circle consisting of eight vertices that was rotated by 22.5° on z-axis in object mode. The quarter circle was made by inserting a vertex on each side to align with the axis and then deleting the rest. You can use CTRL+R then point and click at the space between the circle vertices with your mouse to create one vertex in the middle.