The rake is a common technique in Blues lead guitar. It is used quite often in the C form, particularly by B.B. King. The rake is achieved by first fretting a note and then laying a finger (or fingers) across two or three adjacent strings. The pick is then raked across the strings, causing a muted sound leading up to the original note which is then left ringing. A rake is indicated by an arrow in the tablature pointing up to the note to be raked.
Notice how the rake adds expression to the first note here.
In this example the E is played with the first finger and the damping is done with the second and third fingers.