Doesnt't this sound festive, Balloon Stitch? It is a canvas stitch which I found at Serendipity Needleworks where you can find excellent instructions.
Below is a sequense of my photos:
Increase with one hole over and below.
After four stitches you come to the middle of the design.
Here you make the stitch the same height.
And then you decrease the height again until you have
a square on point.
Repeat the pattern, then work an identical set
above the first row.
Aren't they festive?
Like so many Canvas stitches, the Balloon Stitch eats thread. Can you see a slight difference in the tension of the two light blue stitches on the left? I have changed to Surface Balloon Stitch to save thread, which is easy to see on the reverse, have a look at the photo below.
For upholstery or a cushion that will be used and suffer wear and tear, I would recommend the proper coverage on both front and back, despite the amount of thread that is needed.
Homework: Add here