Here is my design for an affordable easy penny board holder for any sized backpack.
All you will need is:
2 Bungee Chords
1 Set of Grommets with tools
Step 1: Grommet Hole Punching and Setting
First you will need to punch holes where you want your grommets to go. Place a piece of scrap wood inside the backpack so you do not accidentally punch a hole all the way through. Also make sure the sets of holes are not farther apart than your board is long or else there will not be enough tension in the bungees to secure your board. After you are done punching the holes you can now attach your grommets using the tools.
Step 2: Attach Bungee
After you have all your grommets in, simply cut off the ends of your bungee chord and put them under a flame so they do not fray later. Then feed one end through each grommet and knot them on the other side.
Step 3: All Done!
Now just test fit your skateboard to make sure it fits snug. You can adjust the bungee chords as need so the board does not slide around. Have fun!