On the banjo it is easy to create a major chord anywhere on the fretboard by simply flattening the first finger of the left hand and pressing it down across the first four strings. This is called a bar (or barre). By forming a bar at the 5th fret, a C chord can be played as shown in the following diagram.
The following example uses a bar at the 5th fret to create a C chord and then at the 7th fret to create a D chord. Notice the alternating bass pattern in the right hand.