The compartment is a design placed under the shield which shield supporters are standing on. Usually animals or figurs standing on rocks, grassy mount or decorative decor.
AS DESCRIPT in
"A Complete Guide to Heraldry"
Since one's earliest lessons in the rulesc of heraldry, we have been taught, as one of the fundamental
laws of the achievement, that the helmet by its shape and position is indicative of rank; and we early
learnt by rote that the esquire's helmet was of steel and was placed in profile, with the visor closed:
the helmet of the knight and baronet was to be open and affronté; that the helmet of the peer
must be of silver, guarded by grilles and placed in profile; and that the royal helmet was of gold,
with grilles, and affronté.
For me as an heraldry artist it is wonderful to see the diversity of helmets, every Coat of Arms has
their own individual helmet. There are quite a number of different styles of helmets, from stylized,
old style, simple to very elaborated representation - as individual as your Coat of Arms !