The (last) bit of armor protection (or BOAP) rule is introduced in Rifts Ultimate Edition on the right column of both pages 288 and 355
It has informally been referred to via the slang GI Joe rule by fans due to it having effects similar to the cartoon GI Joe where when armor/vehicles were destroyed, the person inside was mostly undamaged.
A related rule on RUE pg 358 also gives similar properties even to SDC items: a destroyed SDC object doesn't protect what is behind it, but the item behind it DOES protect a tertiary target:
- most blasts and beams stop upon hitting their target,
- and if a beam goes all the way through an S.D.C. structure,
- it stops upon hitting whatever is behind the first target.
- The same is true of M.D. projectiles such as rail gun rounds
SUHT ("Stops Upon Hitting Target") could be an easy acronym to discuss the impact of the first line.
SUHWIB ("Stops Upon Hitting Whatever Is Behind") could be a casual way to abbreviate the impact of that rule explained in lines 2 and 3
Page 207 had a less extreme and more specific version of this:
- if there are at least two M.D.C. points left in the armor,
- I will let as much as 20 M.D. be deflected by it
- (21 or more points zaps the armor and the person inside)
This effectively means that the "last 2" function like 20, effectively giving a bonus 18 points of protection for 1 attack only, rather than an unlimited temporary bonus.
This apparently means there is no added protection with only 1 MDC remaining.
Two paragraphs prior to the BOAP rule on RUE 288 is mention that reducing MDC:
- body armor is so battered and full of holes that it is only effective against SDC :weapons,
- and barely that,
- only stopping attacks that are 1-7 to strike.
- An attacker's roll to strike that is 8 or higher hits the body inside the armor