To Join Walls

The wall segments to be joined must be collinear, and their end points, where they are to be joined, must be coincident (occupying the same point in space).

Select ( Join Elements ).
Identify the first wall to join.
Identify the second wall segment to join.
Accept. This is applicable to linear profile too.
Tip: The Join Walls tool can be used to combine multiple collinear walls into a single wall. In some instances this may cause space shapes to become disassociated. Should this happen, use (Update Space) to restore space association with the walls.