Here are the two–string Rock chord shapes for A, A6 and A7. In all three chord shapes only the 5th and 4th strings are strummed. The open 5th string is the root note (A).
A
A6
A7
The open circle with the number 1 inside it indicates that you keep your 1st finger in position even though that note is not being played.
Play the following chord progressions using these rock chord shapes. Use eighth note strums and only play the 5th and 4th strings. When playing power chords, it is common to use only downstrums, as this achieves the best sound.
Here are the previous examples as a two bar pattern.