No leprechauns are safe!
I think that if i use screws as a simple machine my trap will work the best.
How to Make the Trap
The trap will be made by taking two or three toilet paper rolls and using green duct tape to tape them together. After you do that you will carefully add about three screws on one end of the trap. On the other end you will cut a hole in the toilet paper roll going from one side to the other. Once you have done that you will take your green paper and put a big enough hole in the top to be able to tie a string in it. tie the string together and place it above the trap facing longitude. cut a little hole in the middle of the second toilet paper roll and place the string through it. tape the end of the string that is inside toilet paper tube and tape it down with normal tape. Then when the leprechaun goes through it and hits the string the tape will come undone and it will drop the paper. When the paper drops it will trap the leprechaun in the tubes and you would have caught your first leprechaun.
How it will work
When the leprechaun walks in it will hit the string. The string is attached to paper that will then fall when the leprechaun hits the string. Once the paper falls the leprechaun will then be trapped between paper and screws inside toilet paper rolls.