Steel or aluminum plates tying in crossmembers to frame rails. Reduces stress on mounting bolts and stiffens the frame for durability (rigidity).

See Bracket Plates.

1) Fifteenth-century mail sleeves covering the armpits and other portions of the arm not covered by plate armor 2) Sixteenth-century lames at the armpit of the breastplate

Envelopes with expanding accordion pleats for extra capacity.