mirror problem

v2.76 / Windows7

When I mirrored a garment, the center partially overlapped and the vertices didn’t all merge. I’m thinking maybe because the central vertices were not aligned on the z-axis before applying the mirror modifier? Can I select the line of vertices and make a quick adjustment somewhere, or must I align each vertex separately?

Thanks…

The object by default mirrors across its origin so if the origin is not along the centre line then you will get a gap or overlap.

Move the origin
or move the vertices
If you enable clipping in the modifier then it will then stop vertices from cross the centre line

Can I select the line of vertices and make a quick adjustment somewhere, or must I align each vertex separately?
Juts grab and move them