# Mirror Modifier not working with subdivision surface [duplicate]

I created a chair, and added a mirror modifier as well as a subdivision surface modifier. I made sure that the subsurf mod is below the mirror mod, as you can see in the picture below. However, there is still a visible shrink in the mesh at the point where the right and left side of the mirror meet.

I also made sure that the mirror line is at the origin of the object, that all the vertices on the mirror line are indeed merged together, and that the points beside the mirror points are in line (the meeting point is not a v-shape).

This causes there to be a visible line when rendering the image.

How can I fix this problem?

You have to enter Edit Mode (Tab) and then select edge select mode (Ctrl+Tab). Then press N to bring up the Properties panel and set the Mean Crease of the edges along the mirror plane to 1.00.