A Linguistics Workbook, 4th Edition

This rule is characteristic of modern American English. It accounts for the
pronunciation of pitted [phirid] and hottest Bhast]. It is, then, an example of rule
template 3 in which A is t, B is the flapped r, C is a stressed vowel, and D is
another vowel.
There are also rules in which part C of the conditioning environment is present
and part D is absent. An example is the Plural Rule of English (see Linguistics,
pp. 86-90).