Who knows twenty-nine?
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29 tefachim is the midpoint of the height of the Altar in the Beis Hamikdash. This was marked with a red line around the Altar. (Rambam, Hil. Beis Habechirah 2:6-8)
The significance of this demarcation was that the blood of certain offerings had to be applied to the upper half of the Altar, and of others to the lower half.
29 are the consonantal phonemes represented (supposed to be, anyway) by the letters of the alef-beis.
(There are 22 letters; six of them, בג"ד כפ"ת, have plosive and fricative forms, and one, ש, has two different sibilant sounds.)
Though no one I've ever heard of pronounces all 29 of them as distinct sounds.