1) Describes a female’s ass, while standing, you could set a beer can on it. Generally found on Afro-American women. Although their asses are nice, a beercan is rarly found on white, hispanic, or asian women.
2) The obvious - a can used to hold a fermented liquid made of hops and barley.
A door wall is a sliding-glass door or patio door. The term is yet another example of banal Michigan vernacular, where in the residents latch on to company names, trademark names, marketing terms and product names from local companies. The terms become embedded in the local vocabulary and eventually become accepted as actual valid words and phrases. In this case the term comes from Wallside Windows in Taylor, MI (a large window manufacturer), where 'door wall' is their created word for sliding-glass door.
"Bob! John's gonna bring over them doorwalls from Wallsides on Tuesdee afternoon 'round two-thirty. Get 'er done!"