If you are trying to butt to walls together with the same materials on the exterior hatch, try the following to get rid of the vertical line & make the hatch match up (see the attached doc for ref).

Select your wall, right click and choose Edit Wall Style. On the materials tab find the material which is on the outside of the wall which makes your hatch. Double click it & edit it's display properties. Go to the tab at the top "Other" & look for the section 2D Section/Elevation rules & put a check mark in the box for Merge Common Materials. Click OK all the way out. This should eliminate the vertical line. If you have a CMU or Brick hatch pattern, select the wall, right click and choose materials, Add Surface Hatch Override. In a ISO view, adjust your hatch pattern to suit your needs. This also applies to the horizontal line seen between floors stacked on top of each other.