To secure the last vertical warp strand, you tuck its end under the prior wraps on the BACK side of the seat frame, as seen here.  In this image you can see how the strand has been tucked under. This tucked under end is also covering the final nailed in end of the prior warp strand. I realized that I did not adequately photograph this step, so I go into more detail with it when I do the same thing with the final wrap of the horizontal weaving.  You can jump ahead to the Page 8 (and going on to Page 9) to see how this final weave is done and how its loose ends are tucked under.

This image shows the loose end of the last warp strand tucked under at the bottom of the BACK side of the seat frame.

The vertical warp strands are now completed. In this case I have ended up with 49 vertical weaves, which is an ODD number, which is what I need. It does not matter how many strands you have, so long as it is an ODD number of strands, and that essentially all of the space on the top and bottom of the chair frame is filled in with strands/wraps so that there is no gaps.

Starting on the horizontal weaving, you will also need to put in an initial wrap of rattan, as seen here on the top left side of the seat back frame.  However, you can see in this image that this time I have made an extra wrap, compared to what we did for the vertical warp strands.  This is because there will be two wraps that divide each horizontal weave, as opposed to the single wrap that was between each of the vertical weaves.

You also add this initial wrap to the right side of the chair frame.