Automatic Man Trap
 
Alvin's greatest invention in The Marvelous Inventions of Alvin Fernald  was his Automatic Man Trap.   This invention had many parts and required all the efforts of Alvin, Shoie and The Pest to properly make it work.  Alvin's original list of supplies included:
 
 
Fireplace Bellows Pulley
Popcorn Gunny Sacks
Pepper Hammer
Long Rope Nails
Several Short Ropes Shovel
Strong String Knife
 
We won't tell you exactly how it all came together (we don't want to ruin it if you haven't read the book), but we will describe what shape the "Bad Guys" were in when the police found them:

"A powerful light had been brought from a squad car and was shining on the front porch.  One of the officers had recovered the man from the tree.  The man was sitting on the steps, his eyes bulging, still gasping for breath.

Another officer was working over the second man.  'Say,' he called, tugging at the man's clothing, trying to rip it loose, 'this isn't a bad invention.  Maybe we should use it instead of handcuffs.  Looks like it will take me fifteen minutes, just to pry this fellow loose from the floor.'"