Its a knex Jumping Thingy

Step 1: Ingredients

THese are the pieces you will need for making a J-T.
I think you can get these pieces in most knex sets.

Step 2: The..top Part.

wrap two rubber-bands around the side holesin the red things. The green rods just make it look cooler.

Step 3: The Shooty Part

To make the part that actually moves the J-T, take a blue rod, and add 5 orange rods. It is important that you have that space between the 4th and 5th orange thingies.

Step 4: Attach

Attach the top to the launcher like in the picture. remember to add andother blue rod...

Step 5: Final Step..

add the grey rodthrough the circle in the orange things, and attach it to the red thing.aim the straight up on the ground,pull the orange thingy down, and let go. it should only go up about a foot, but you could use different kinds of rubber bands and see what kind is best...