Stuff you need:
Duck tape or glue
A box with lid
A paper clip
A tech deck
Step 1: The cutting
Cut your card untill it bends into a halfpipe in your box
Then cut a rectangle or square of any sise out of it (I'd mark the rectangle if I were you)
Cut lots of duck tape if you are using it
Step 2: Sticking the card
Then stick one end of the card to one side and the other end to the other!
Make sure the middle sticks too!
I didn't have duck tape or glue left when I had finished so I had to do this pic in paint
\/ ( The gray is the tape)
Step 3: The grind rail
For this make Apiece of card curved or a paper clip curved
Then curl up small pieces of the cut card and tape or glue it to the paper clip or card
Now stick it to the box where theres a space so it blocks off the corner
Step 4: And you finished
If you dont want to make it the same as me you don't have to
You can make it different just cut the card different or add stuff I only had a small bow so I couldn't make loads!