Kaf

ך כ
Kaf occurs frequently in its prefix and suffix roles. In its final form, besides being the last letter of some common words like king מלך and way דרך and walk הלך, it is the ubiquitous second person singular personal pronoun suffix.

Ruth 1:15 has many examples of ך
here it is twice as the second person singular pronoun as object of the verb

וַתֹּאמֶר רוּת אַל-תִּפְגְּעִי-בִי לְעָזְבֵךְ לָשׁוּב מֵאַחֲרָיִך

 vàto)mer rvut )àl-tipg`y-by l`azbék lashvub mé)àxarayik 
and Ruth said, do not force me to leave you, to turn back from following you

and in the next example it is as the last letter of the root ילך - the first occurrence is second person singular feminine, the second occurrence first person singular (both imperfect). The final form appears in the second instance since the word ends there. The non-final form appears in the first instance because of the feminine suffix that is part of the imperfect. (Note also the first letter of the common conjunction, ki, indicating cause or reason or just a particular form of coordination.)

כִּי אֶל-אֲשֶׁר תֵּלְכִי אֵלֵךְ וּבַאֲשֶׁר תָּלִינִי אָלִין
ky )el-)asher télky )élék vubà)asher talyny )alyn
for wherever you go I will go and in whatever you stop over I stop over

and in these two statements, it is the possessive second person singular pronoun 

עַמֵּךְ עַמִּי וֵאלֹהַיִךְ אֱלֹהָי
`àmék `àmy  vé)lohàyik )elohay 
your people my people your God my God

I have not colored green all the grammatical letters above - I wonder how quickly recognition will become automatic.

Now to look at the prefix Kaf in Ruth, here are some of its uses. The first is in Ruth 1:4

וַיֵּשְׁבוּ שָׁם כְּעֶשֶׂר שָׁנִים

 vàyéshbvu sham k`ser shanym
and they lived there about 10 years

Usually I think of the prefixed kaf as the word 'like' or 'as' but as with all prepositions, it refuses to stay in one box.

יעשה יְהוָה עִמָּכֶם חֶסֶד
כַּאֲשֶׁר עֲשִׂיתֶם עִם-הַמֵּתִים וְעִמָּדִי
y`aseh yy `imakem xsed
 kà)asher `asytem `im-hàmétym v`imady

may יְהוָה deal with you with mercy

as you have dealt with those who died and with me

In its role as 'as' it is perilously close to the separate conjunction ki, also used in Ruth of course and very common - about 27 times in this story alone, as common as the use of  'for' in English. In the above verse, unmarked, there is another use of kaf as a grammatical letter - the first letter of the suffix כֶם meaning you plural masculine or in this case the possible dual feminine. - Let's wait for mem and nun before pursuing this lead. I don't want to make things up without examples.