You could try inserting a small Line(s) (size experimental to start with) and position two on the left and two on the right. One at 9.9 cm (third of page) and one at 19.8 cm (two thirds of page).
The initial created line is copied when it has been positioned, and then pasted so we have four lines in total (in my example). Two on the left side and two on the right side.
Click the image below to see how I have achieved this.