Watch the Scratches online guitar lesson by Chris Buono from 60 Electric Guitar Techniques You MUST Know
A percussive strumming technique known as scratches or "chanking" is great way to vary up your rhythm playing while adding a new tonal element. Most importantly, it serves as a way to create rhythms with syncopation that would otherwise be difficult or nearly impossible to play. While the go-to style this technique is often associated with is funk, scratches are used to play within almost every style of music with varied approaches and prominence. Simply laying a fret hand finger or more over the intended strings to be attacked, it takes but a soft touch to produce the desired effect. Not too soft though, or otherwise you'll allow open strings to ring through. At the same time, a touch that's too heavy will defeat the intent and result in fretting the very notes you're trying scratch out!