There are 316 4-letter words containing F in the ENABLE dictionary — 8% of all 3,903 words at this length. At 4 points, F is worth more than most tiles without being awkward enough to hold back for — it is generally better placed than saved.
The F falls in the first position more often than any other, in 191 of them. 33 of them use the letter more than once — baff, biff, boff, buff among them, which is the case worth checking twice when a game has told you a letter is present but not how many times.
If you know more than one letter, this page stops being the fast way to find it. Enter what you have in the unscrambler — the Contains, Starts with and Ends with filters combine, and setting both length fields to 4 narrows this list to the handful your letters actually allow.
Where the F sits
F in the first position (191)
face fact fade fado fads fags fail fain fair fake fall falx fame fane fang fano fans fard fare farl farm faro fart fash fast fate fats faun faux fava fave fawn fays faze feal fear feat feck feds feed feel fees feet fehs fell felt feme fems fend fens feod fere fern fess feta fete fets feud feus fiar fiat fibs fice fico fido fids fief fife figs fila file fill film filo fils find fine fink fino fins fire firm firn firs fisc fish fist fits five fixt fizz flab flag flak flam flan flap flat flaw flax flay flea fled flee flew flex fley flic flip flit floc floe flog flop flow flub flue flus flux foal foam fobs foci foes fogs fogy fohn foil foin fold folk fond fons font food fool foot fops fora forb ford fore fork form fort foss foul four fowl foxy foys fozy frae frag frap frat fray free fret frig frit friz froe frog from frow frug fubs fuci fuck fuds fuel fugs fugu fuji full fume fumy fund funk funs furl furs fury fuse fuss futz fuze fuzz fyce fyke