F, retitled Mister (or Mr.) F in some cases, has the thinnest of plots - a man, F, sends various women out to clients with various sexual needs. The last two segments of the film abandon this entirely, along with the F character, suddenly introducing us to his brother, and finally, a co-worker (I guess) of his brother's, both of whom sample the wares of the ladies working for F. I'm making this seem more coherent than the film does.
This film was clearly made at a time when softcore porn felt the inexorable shift to hardcore, but still didn't want to go full in. Instead, the most unsimulated content you get is fellatio, and almost every time the camera painstakingly cuts away (usually panning down to beaver shots). The first two segments, both starring Levi Richards as a horny client, are the most natural both in prattle between performers and in making the contrived body positions slightly less absurd (I guess Richards being such a pro helped). After this it's all downhill, with lots of clunky dialogue (many occasions of the women reminding each other how nice this is, and the men telling us they are pulling the covers town to see what the women look like) and even clunkier "sex." The nadir is a threesome with an escort and a couple where the woman playing the escort works very hard to avoid sexual interaction with her partners (giving tentative licks to the man's member and taking the term "sit on your face" too literally as she just lets the woman...sit on her face, with not much else going on). This is cut short, lost to the ravages of time or a merciful editor, but the next segment isn't a great deal better, culminating with the man face down, ass up, as two women somewhat perfunctorily try for a few muted cheek kisses and not what such a position would be expected to lead to in porn.
The F-brother scene is more of the same, with a woman who is hesitant to do anything but get a grip as the man fake yells (and as a bonus we get more shots of her bare back or the top of her skirt than you'd expect in some attempt at showcasing intercourse), but the final scene is at least a fairly interesting way to leave, as the woman is reading an adult magazine and, with choppy blonde hair and large pink areola, stands out compared to the other more interchangeable ladies in the film.