I want to merge two vertices into one, but Blender help me to select the third one automatically. I didn't turn one Proportional Editing Mode. Would anyone here can explain why? Please go to my shared videos below to see my problem in detail, if my word is not clear enough. Thank you
https://drive.google.com/file/d/0B7o5ywq5dlOgOFNVVHhkZzljcjQ/view?usp=sharing