my 68 cuda engine compartment

Its called a toothed washer. They are available internal or external tooth. The washer belong on top of ring terminal between it and the nut of bolt head. To place a toothed washer on the paint limits to currecnt path to ever how many little teeth cut through the paint.
We had a rash of 90 model Fords come back for "intermittent fails to start" because the toothed washer at negitive battery cable to block connection was placed wrong.