Dip Sticking applies to checking for understanding on the fly. For example your lecturing and you've covered an vital concept. Taking a moment and checking to see how well the students understand is dip sticking.
The advantage of dip sticking gives teachers the opportunity to adjust their lesson on the fly to meet the needs of the students. Waiting to the end of a chapter or unit to test is often too late. There are multiple ways a teacher can dip stick refers to the strategies tap for more.