When your wife is a whore that can't make it through your military tour without getting dick, so she ends up obtaining a boyfriend to fill in her dickspace despite her marital vows.
My boyfriend-in-law fucks my wife while I go fight for my country.
How you are introduced to people at a party by your girlfriends sister, when the parties in question are over 21 years old and very committed to each other.
Hey Sally, this is my Boyfriend-In-Law,(name), and hopefully soon he will make my sister an honest woman.
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!"