Here we have a grid set with a vertical to a one stride, to a Swedish oxer, to a one stride, to a vertical.
A swedish oxer includes 4 standards and at least 2 poles. The poles on the front set of standards are set with one side higher than the other. The second set of standards also have one side set higher than the other on the opposite sides from the front.
The swedish oxer helps to improve straightness because the lowest part of the jump is in the middle. The higher points on the sides also encourage the horse to pick his legs up higher.
I did not do much height with this exercise since Grady has not been jumping much since hurricane Irma. It took a while to drag all the jumps back out to the ring and it is still a work in progress.
If I were to add height, I would have left the verticals lower and used them more to place my horses stride away from the oxer and give him room. You could also replace the verticals with cross rails to create more of a chute and encourage even more straightness.
Try this exercise at home and let us know what you think!