For the mesh to match where the welds meet the horizontal and vertical parts, we must create more intersections. Refer to the image below for guidance.
Click Draw Modify Intersect.
Click the diagonal line of the upper weld (A) and press Enter.
Click the upper-right vertical line of the vertical part (B), click the upper-horizontal line of the horizontal part (C), and press Enter.
Click Draw Modify Intersect.
Click the diagonal line of the lower weld (D) and press Enter.
Click the lower-right vertical line of the vertical part (E), click the lower-horizontal line of the horizontal part (F), and press Enter.