- Marker Caps, about 4 or 5
- Fake Blood
Remove the caps from your pens or markers because that's pretty much all you'll be needing for this prank besides fake blood.
Fill each cap with fake blood and make sure to fill it to the top
Carefully clip each single cap on the window blinds. Make sure that the blood portion of the caps are hidden in the back, so all that will be barely visible will be the clips of caps. It's also a good idea to spread them apart and try not to clip them all on the same row.
By now, the prank is ready.
With all the blood filled caps in place, all you do is wait for someone to open the blinds. When that happens the caps will be flipped over cause all the blood inside to come dripping out, making a cool and creepy Halloween Effect.