ck /k/
Core Rule
ck represents /k/. It appears after a short vowel, usually at the end of a word or syllable, to lock in the short vowel, as in buck. It is one sound, not /k/+/k/.
Articulation
/k/ is a voiceless velar stop: raise the back of the tongue to the soft palate, stop the airflow briefly, then release without voicing.
Examples
buck: short /ʌ/ + ck prevents vowel lengthening. fuck follows the same pattern. In jacket, /k/ is spelled k because it comes before e; ck is not allowed there.
Pitfalls
Do not use ck before e, i, y; ck mainly follows stressed short vowels.
Phonics Breakdown
Back of tongue to soft palate, brief stop, release air, no voicing.