First of all, note that the vertical support is positioned BEHIND the horizontal support.
Starting from the bottom right, the strand runs up to the left, around the vertical support (dotted line), down to the left, around the vertical support, OVER the starting strand and then UNDER the cross formed in the center of the pattern.
As shown in the sketch, ensure that the cross is applied to the convex part of the horizontal support. Tighten by pulling both ends tightly at the same time.