Some might say its cruel, but then so is a mouse trap, poison is a slow and painful death and an air rifle pellet to the head is a difficult shot with two bikes and a classic car in the garage.
But this method is no risk to anyone, and to be honest is quite exciting going out to the garage/shed in the mornings.
You need to be careful to get the balance right on the batten or wooded ruler plus a small amount of crumbs around the bench end of ruler and a line of biscuit crumbs along ruler leading to 1/2 biscuit balance at the end of the ruler.
The rest is self explanatory and it works much to my delight.