Watch the Frailing 2 online guitar lesson by Matthieu Brandt from Slap, Frail, & Thump
Frailing is a percussive picking technique that is used by banjo players among others. Old time country banjo players use a technique called 'clawhammer' in which frailing is used, but it's also used by bluegrass players and singer-songwriters as a rhythmic backup.
The Jam button will play you Example 113.
Listen to 'Blackbird' by Paul McCartney or JJ Cale