What angle must the blade be? Is it good to have a high attack angle, or one that’s nearly flat?

How heavy should the apparatus holding the blade be? How far should it travel? Is keen sharpening important, or does the weight do most of the work? What kind of latch/release do you use?

Lastly, morbid extra credit, did they ever execute someone with their face up, so they could see the blade coming?

EDIT FOR CLARITY: Way more complex than an axe or a noose.