Give Us Our Daily Sex (1979)

Sinopsis: A pair of sexy bisexual nurses live in an apartment building, one floor up from a middle-aged couple and their son Albert, who is busy putting his new science project—a periscope—to good use by spying on the lingerie-wearing lovelies. Meanwhile, Albert’s mother is being even naughtier than her precious boy, sneaking off for some extra-marital action while her hair-obsessed husband is at the salon, having his follicles tended to. There are multiple versions of this movie - the original softcore version as well as a harder one with inserts of intimate close-ups performed by body-doubles.