Ska stroke

The ska stroke or ska upstroke, skank or bang, is a guitar strumming technique that is used mostly in the performance of ska, rocksteady, and reggae music. "Reggae is most easily recognized by...the skank." Ska strokes serve as a rhythmic base to a song, and may be doubled by the drums. This style of playing has a dance associated with it, the skank. In reggae, the guitar usually plays a short, percussive, "scratchy chop sound [chord]," on beats 2 and 4 (1234), often supported by staccato piano (late 60s to the early 80s) or synthesizer. Play 

Ska strokes create a bouncing rhythm, going up then down in pitch. Played in 4/4 time (𝄆1 & 2 & 3 & 4 & 𝄇), the chosen guitar chord is played on the downbeat (#'s rather than &'s), and then a ghost note is played on the upbeat (&'s rather than #'s) by lifting the left hand off the fret a few millimeters. However most traditional ska is focused on the upbeat, playing on the downbeat is more closely associated with reggae, where the ska strokes are played much slower as opposed to ska.