In case the question is concerning the height of the wall in the middle piece of fence, I would like to answer with a visual argument. I suppose this is a matter of symmetry and repetition. On the one hand, since the piece of fence that is between the path from the main entrance and the driveway is not as wide as the separations between the piers on the left side of the fence, it would be an irregularity to have the piers closer to each other there. On the other hand, making it a solid fence would perhaps break even more with the style, as the side of the garden that is facing us is for the rest built up just from piers.
Adding one more option, these would be my considerations.
- Build two poles through which the hedge towards the house is visible. The only argument against is that the separation is not
continuous, but then again, neither is the fence at that point, so I
would go for this one of the first two options.
- Build a solid piece of fence wall between the driveway and the path. This would break with the repetition of piers, but would
maintain just a single separation width. I find the pier theme
visually more important than the continuous separation, and would
thus not vote for this.
- Change either the width of the mid piece or the separation between the piers for consistency. By making the piece of fence we're
discussing as wide as it needs to be to have the same separation
between the piers as we see on the left side, or making this
separation on the left less, I would say maximal consistency is
In case your question concerns the height of the the wall between the piers over the whole front of the fence, I would say it depends on its thickness or depth. If the wall is as thick as the piers are, I would vote for a height that is the same as the width and thickness of the piers (say, horizontal piers in between). If the wall is thinner, it would depend on the final height of the hedge. With a higher hedge, a higher wall would be better, a hedge as low as is displayed wouldn't invite for anything higher than at max half the height of the piers.
This is all just based on my intuition of what seems more attractive to the eye (which seems the primary concern to me), I would love to hear other arguments.