Join Sculpted Meshes

I recall watching a time lapse of sculpting, where the guy was working on two separate pieces, and at one point, he appeared to magically zip them together, and continued sculpting. Anyone know how to do this?

Could he have been sculpting with the mirror modifier on, with merge and clip checked? Either that or between frames he did a bridge and didn’t show it… Can you link to the video?

ther is this addon here >>> http://blenderaddonlist.blogspot.jp/2014/06/addon-multi-edit.html