D rings are a type of ring comonly used to get a zero leakby seal on accumulators.
They are literally shaped like D and are solid with no gap so they seal better than teflon type that overlap on the ends or interlocking rings.
If you use D rings and block the accumulator, that's it. (zero leakby)
Same as if you went to all the trouble to block off all the ports in the case.
