I'm in the process of replacing some of the switches and surface
moulded boxes in our house for cosmetic reasons. Some of the switches
are really dirty, scratched etc and some the moulded surface boxes are
cracked etc.

Anyway I have a question and I know its going to sound really stupid
to alot of you. But what is the best of breaking the knockouts on the
moulded boxes to ensure clean straight edges. The first one I tried I
used a pair of plier but it was a bit of a mess - good job they are so
cheap.
Am I missing something here. Is there a recommended way.

Many thanks!