No more sliced knuckles.
Image from Cycling Weapon of Mass Destruction.
Changing chain rings always seems like a great idea, and it usually seems to go well until you're down to the last couple of bolts when suddenly in less than a blink of an eye you've exposed the bone on two knuckles.
I once made a tool out of an old hacksaw blade that helped keep the bolts steady, but it didn't completely save my knuckles - and the hacksaw blade was pretty uncomfy to hold...