Margarita, I do know that when marking multiple parallel lines that you want to be all the same distance apart and fit into a set space, it is better to put a tape measure or ruler along one edge and mark the increments using either pins (which I would do in this case) or pencil marks (for paper). Then repeat the same process on the other side of the void, and finally join the dots.
This is because I have found that if you just mark one line and then using the parallel lines on your quilter's ruler to put in the rest, you will get slightly over sized parallel lines (it can be as small as the width of the drawn line) and the discrepency is accumulative (gets worse as you go along). (I have had this happen to me when cutting bias tape
)
Whereas if you mark the distances with pins, you can easily check that you have the right amount of divisions, and should you just have a small amount of gap left over where it shouldn't be, you can just move the pins a little bit along until you have lost the excess and the gaps visually look right. I ended up doing this on at least one of the borders on Caught Redhanded, to get the quilting to fit the distances properly.