This is super simple.
-Out of sturdy fabric, cut out 4" x 22" rectangles. You can use canvas or denim or any other fairly thick fabric.
-Fold in half (hotdog) and iron a nice sturdy fold.
-Open it up, bring each edge into the center line and iron the new folds you've made.
-Close up along center fold...
and sew along edges to secure
Yep, that's it.