Spolas? "Subarmalis"?

[Dan Howard]

The armour isn't susceptible to thrusting attacks from any angle unless there is a gap - such as the armpit. It is hard to describe, but the weight of the plates help to hold the overlapping plates snugly close. You can't get an arrow or spearhead between the overlapping plates unless the warrior is prone or the weight is taken off the bottom plate in some other fashion (e.g. grab it and hold it up)