Kako writes the consonant k and takes the numeral forty. Its name is a Slavonic adverb meaning how, and it opens a further stretch of the recited alphabet, the part that has been read as a question and an instruction and about which the reference literature is more cautious than it is about the opening.
The sound is a plain velar stop, and in Slavonic it participates in the alternations that produced several of the letters earlier in the order. Where k stands before certain front vowels in a related form it softens, and the softened result is written with one of the affricate letters further down the alphabet. A reader who has learned those alternations can often see the same root behind two spellings that look unrelated on the page, which is one of the ordinary skills of reading Old Church Slavonic.
The numeral forty is reached by counting the Glagolitic letters in order, this being the thirteenth sign and the fourth of the tens.
The letter is common in every kind of Slavonic text, and it is one of the signs whose rounded and angular forms differ enough that a reader coming to a Croatian missal from the gospel codices has to relearn it. Both hands are Glagolitic, separated by centuries and by the change from a book script to a script also used for charters and inscriptions.