The tap is the brief break and re-establishment of contact by the hand at a placement on the face (mouth, chin, throat) when a syllable at that same placement immediately follows. For example, when cueing boo boo, the cuer places handshape 4 at the chin for the first syllable, but must release contact — briefly removing the hand from the chin placement in order to contact the chin again for the second syllable. A handshape may not maintain contact with a placement from one syllable to the next.
The tap is similar to the flick. However, the necessity to tap is based on an immediate reoccurence of a placement and happens regardless of handshape. In other words, when cueing, birdie, the cuer must tap because the mouth placement is used in consecutive syllables. The transition from handshape 4 to handshape 1 occurs after the hand has left the placement and must be complete before it contacts the mouth placement again. The tap is unlike the flick in that, flick are required only when the same handshape occurs at the side and in sucession without a vowel occuring between the handshapes.
The tap is important for synchronization. The production of manual cues must be timed to occur with the corresponding information on the mouth. The physical touching of placements on the face provides by tactile feedback to the cuer that can be used to help synchronize with articulation of vowels on the mouth.