First the materials:
A bic pen
Any kind or Nerf dart
Duct tape or electrical tape
A Nerf gun
A pocket knife
First get the Nerf dart and rip off the tip, or head.
Next get the bic pen, take off it's bottom cap and pen cap and inc tube so it looks like a tube.
Next Insert the bic pen tube into the Nerf dart.
Then put some tape on the dart so the pen doesn't slide off.