Four square junction box eccentric holes???
1)Referring to a metal junction box say 4 square by 2.125 deep, When is a pigtail needed to be attached from the junction box to the equip grounding conductor? Is it only needed when more than one knockout on the junction box is used to run EMT to it?
2)WHy are some junction boxes knockouts concentric like pictured here from Home Depot:
3)And why are some junction box knockouts eccentric like pictured here: