How to get SubD edges to stick together

Many times when I draw a face with an edge that is coincident with another edge, they don’t become the same edge. I’ve tried stitch and join but neither of those does it. There must be an easy way?


and

if the edges are truly coincident join will work.

if not, stitch will

select a pair of edges then run the stitch command, pick the location and then enter to complete.

can you post a file or pics to show where your problem lies?

I think you are right. When I am more careful, it looks like it works. Thank you.