I made a 3D sketch and then used the weldment toolbar to put in some angle structural pieces. Then I sketched a line and inserted a squaretube. I wanted to do a coincident mate reference of the top side of the angle and the top side of the sq. tube. I highlight both surfaces. No mate. I am not experienced. Can anyone tell me what I may be doing wrong. I am using the weldment toolbar and related icons. Help is appreciated.