From tv reruns:
What part of “stop the car” don’t you understand? (Bones)
What part of stay don’t you understand? (NCIS)
What part of “desk work” don’t you understand? (NCIS)
What part of “Level 5 sorceress” don’t you understand? (NCIS)
The first three are sarcastic, using the snowclone template “What part of X don’t you understand?” (where X is a linguistic expression), conveying that the meaning of X should be obvious to anyone, despite the fact that the addressee has apparently not understood it. The fourth uses the formula, but now with reference to an X whose meaning can’t be expected to be generally known, so that the question comes close to being a straightforward information question (though with a somewhat snarky tone attributable to the snowclone).
In a final development, the formula gets used for literal questions about some topic X, as in
What part of beer don’t you understand?
on the Real Beer site, which offers information about beers, brewing, and related topics. (Similarly on a BMW parts site.)
Some more examples, and some reflections on the model for the snowclone, “What part of No don’t you understand?”